I had the hold on exactly the word "surplus", but I discredited option E because I interpreted the sentence as the bacteria gives ALL ITS NITROGEN, INCLUDING THE SURPLUS to the legumes. Does surplus inherently mean that the noun associated with it will be using it for its own purpose?

Can someone explain Q25?

I was initially torn between C and E, then the 2nd paragraph made me confused and I thought the research was based on the bacteria and so chose B. The answer was D.

can someone explain why in the 22nd question option b and c are incorrect.
also the 25th and 27th

25. According to the passage, the ultimate goal of the current research on nitrogen fixation is to develop

(A) strains of Rhizobium that can enter into symbioses with existing varieties of wheat,rice, and other nonlegumes
(B) strains of Rhizobium that produce more ammonia for leguminous host plants than do any of the strains presently known
(C) varieties of wheat, rice, and other nonlegumes that yield as much as do existing varieties, but require less nitrogen
(D) varieties of wheat, rice, and other nonlegumes that maintain an adequate symbiotic relationship with nitrogen-fixing bacteria and produce high yields
(E) high-yielding varieties of wheat, rice, and other nonlegumes that are genetically equipped to fix nitrogen from the air without the aid of bacteria


Unfortunately, most of the major food crops - including maize, wheat, rice, and potatoes - cannot. On the contrary, many of the high-yielding hybrid varieties of these food crops bred during the Green Revolution of the 1960's were selected specifically to give high yields in response to generous applications of nitrogen fertilizer.This poses an additional, formidable challenge to plant geneticists: they must work on enhancing fixation within the existing symbioses.

The above section of the passage tells you that most of the major food crops are unable to perform nitrogen fixation. However, they were selected during the revolution to produce high yields. Since they are unable to perform the necessary fixation, more research is needed to make them susceptible to nitrogen fixation so that they can produce high yields.

Only D matches with the idea.

E is wrong because bacteria is crucial to the fixation process.

C is wrong because the section says they need to focus on enhancing fixation which would require more nitrogen.

Hope it is clearer now.

22) B is wrong because the passage doesn't say that some strains of the bacteria are not capable to entering symbiosis. Instead, it says as a matter of fact, there is a specific strain of Rhizobium for each species of legume.

25) read my explanation above

27) The passage talks about how non legumes plants can be injected with the genetically modified genes that are found in legumes. The reason is that non-legumes are unable to perform nitrogen-fixation on their own.

Having this concept in mind, D matches with the idea. Because, it says changing the genes of plants (non-legumes) that cannot live in saline water, using genes of plants that are susceptible to salinity (legumes).

Let me know if you have any questions.

20. The primary purpose of the passage is to

(D) explain the reasons for and the objectives of current research on nitrogen-fixing symbioses-
correct- this is the broad idea behind writing the passage.

21. According to the passage, there is currently no strain of Rhizobium that can enter into a symbiosis with
(C) maize
correct- The leguminous plants... such as soybeans, peas, alfalfa, and clover - have solved the nitrogen supply problem

22. The passage implies that which of the following is true of the bacterial genus Rhizobium?

(E) Rhizobium bacteria produce some ammonia for their own purposes.
correct- the host plant.... receives surplus ammonia in exchange

23. It can be inferred from the passage that which of the following was the most influential factor in bringing about intensified research on nitrogen fixation?

(B) The persistent upward surge in natural gas prices
correct- Para 1-

24. Which of the following situations is most closely analogous to the situation described by the author as one of nature's great ironies?

(C) That of shipwrecked sailors at sea in a lifeboat, with one flask of drinking water to share among them
correct- Abundance of something which you can not utilize unless you have the mechanism to use it


25. According to the passage, the ultimate goal of the current research on nitrogen fixation is to develop
POE
(D) varieties of wheat, rice, and other nonlegumes that maintain an adequate symbiotic relationship with nitrogen-fixing bacteria and produce high yields
Correct
(E) high-yielding varieties of wheat, rice, and other nonlegumes that are genetically equipped to fix nitrogen from the air without the aid of bacteria
incorrect- without the aid of bacteria

26. The author regards the research program under discussion as

(B) necessary and ambitious but vulnerable to failure
correct- The overall task looks forbidding, but the stakes are too high not to undertake it.

27. Most nearly parallel, in its fundamental approach, to the research program described in the passage would be a program designed to

(D) change the genetic makeup of food plants that cannot live in water with high salinity, using genes from plants adapted to saltwater
correct- comparable to taking genes from legumes and using for non-legumes
(E) develop, through genetic engineering, a genetic configuration for the major food plants that
improve the storage characteristics of the edible portion of the plants
close but incorrect- D is more suitable.

I think this is the sentence that really solidifies it.

Unless they succeed, the yield gains of the Green Revolution will be largely lost even if the genes in legumes that equip those plants to enter into a symbiosis with nitrogen fixers are identified and isolated, and even if the transfer of those gene complexes, once they are found, becomes possible. The overall task looks forbidding, but the stakes are too high not to undertake it.

20. The primary purpose of the passage is to

(A) expose the fragile nature of the foundations on which the high yields of modern agriculture rest
Wrong. High yielding is only being talked about in third paragraph as a contrary to the argument. High Yields are linked to Greenrevolution which forms a conclusion.

(B) argue that genetic engineering promises to lead to even higher yields than are achievable with synthetic fertilizers
Yes it is true, but it doesn’t explains the whole paragraph.

(C) argue that the capacity for nitrogen-fixing symbioses is transferable to nonleguminous plants
Wrong, it can only transfer to leguminous plants

(D) explain the reasons for and the objectives of current research on nitrogen-fixing symbioses
Right, throughout the pass, the author is describing as to why and how are we conducting our research on nitrogen fixing symbiosis.

(E) describe the nature of the genes that regulate the symbiosis between legumes and certain bacteria

Wrong, Nature of genes have not been described in the passage.

21. According to the passage, there is currently no strain of Rhizobium that can enter into a symbiosis with

(A) alfalfa
(B) clover
(C) maize
(D) peas
(E) soybeans

The leguminous plants - among them crop plants such as soybeans, peas, alfalfa, and clover - have solved the nitrogen supply problem by entering into a symbiotic relationship with the bacterial genus Rhizobium


22. The passage implies that which of the following is true of the bacterial genus Rhizobium?

(A) Rhizobium bacteria are found primarily in nitrogen-depleted soils.
No mention of specific place has been mentioned in the passage.

(B) Some strains of Rhizobium are not capable of entering into a symbiosis with any plant.
Wrong, It has been mentioned that is is capable of entering into symbiosis with any plant, but it has not been mentioned that it can’t

(C) Newly bred varieties of legumes cannot be hosts to any strain of Rhizobium.
Wrong, No mention of such statement.

(D) Rhizobium bacteria cannot survive outside the protected habitat provided by host plants.
Wrong, confusing one. But in the passage it says that the plants provide safe habitat but it does not say anything about bacteria not serving outside their comfort zone.

(E) Rhizobium bacteria produce some ammonia for their own purposes.
Right, “Surplus” has been mentioned in the passage, which they also produce ammonia for their own purpose.

23. It can be inferred from the passage that which of the following was the most influential factor in bringing about intensified research on nitrogen fixation?

A)The high yields of the Green Revolution[
Wrong. The Green Revolution was the consequence and not the cause.

(B) The persistent upward surge in natural gas prices
Right. It has not been explicitly mentioned but yes they do say that nitrogen fertiliser prices is directly linked with their natural gas price.

(C) The variety of Rhizobium strains
Wrong. This is not the cause but the research workflow.

(D) The mechanisation of modern agriculture
Wrong. This is out of scope.

(E) The environmental ill effects of synthetic fertilisers
Wrong. Nothing of such is mentioned in the passage.


24. Which of the following situations is most closely analogous to the situation described by the author as one of nature's great ironies?

That of a fanner whose crops have failed because the normal midseason rains did not materialise and no preparations for irrigation had been made
Wrong. The crops were not already in water and thus because there was no rain, it could not materialise.
(B) That of a long-distance runner who loses a marathon race because of a wrong turn that cost him twenty seconds
Wrong, This is not an irony but a consequence of an act.

(C) That of shipwrecked sailors at sea in a lifeboat, with one flask of drinking water to share among them
Right. You are in middle of a sea but still have only one flask of drinking water.

(D) That of a motorist who runs out of gas a mere five miles from the nearest gas station .
Wrong. If motorist would have been solar energy and then it would have been out of fuel, then yes it would be paradox.

(E) That of travellers who want to reach their destination as fast and as cheaply as possible, but find that cost increases as travel speed increases
Wrong. This is not a paradox but a logic.

25. According to the passage, the ultimate goal of the current research on nitrogen fixation is to develop

strains of Rhizobium that can enter into symbioses with existing varieties of wheat,rice, and other non-legumes
Wrong. That is not the ultimate goal, but a part of research.

(B) strains of Rhizobium that produce more ammonia for leguminous host plants than do any of the strains presently known
Wrong. Again it is not the goal, but a part of research.

(C) varieties of wheat, rice, and other non-legumes that yield as much as do existing varieties, but require less nitrogen
Wrong. These yields cannot yield as much as existing varieties do.

(D) varieties of wheat, rice, and other non-legumes that maintain an adequate symbiotic relationship with nitrogen-fixing bacteria and produce high yields
Right. Though this cannot yield but can at least maintain.

(E) high-yielding varieties of wheat, rice, and other non-legumes that are genetically equipped to fix nitrogen from the air without the aid of bacteria
Wrong. This is a conclusion and not the objective of research.


26. The author regards the research program under discussion as

original and extensive but ill-defined as to method
Wrong. It is original but its not ill-defined as it is showing results.

(B) necessary and ambitious but vulnerable to failure
Right. It is necessary but also the stakes are very high.

(C) cogent and worthwhile but severely underfunded
Wrong. No topic of funding ha been discusses.

(D) prohibitively expensive but conceptually elegant
Wrong. No concept of funding as been discusses.

(E) theoretically fascinating but practically useless
Wrong. Nothing of such has been mentioned in the post.

27. Most nearly parallel, in its fundamental approach, to the research program described in the passage would be a program designed to

achieve greater frost resistance in frost-tender food plants by means of selective breeding, thereby expanding those plants' area of cultivation
Wrong. The research is being done for all the plants and not only selective breeding. ( Wrong )

(B) achieve greater yields from food plants by interplanting crop plants that are mutually beneficial
Wrong. This is tempting but it is wrong, as they interplanting crop plants where as in the passage they changing their genetics.

(C) find inexpensive and abundant natural substances that could, without reducing yields, be substituted for expensive synthetic fertilisers
Wrong. This is tempting, but this is an objective and not a research.

(D) change the genetic makeup of food plants that cannot live in water with high salinity, using genes from plants adapted to saltwater
Right. They are changing the genetics of food plants to adapt.

(E) develop, through genetic engineering, a genetic configuration for the major food plants that improve the storage characteristics of the edible portion of the plants
Wrong. Nothing has been told about the edible portion.

11min..6/8..how long should I spend in long RC passages?

Your timing is good. With 4 questions in actuality, it should be 90sec per question on average.

Here is a Carcass 's guide for you: https://gre.myprepclub.com/forum/gre-time- ... tml#p57077