Can we please add the timer and options tab here Carcass? Thanks.

The point here is about transmutation of other metals to make copper. Hence, the para says that it is hard to quantify the amount of actual copper created.

The actual argument in the paragraph is actually the first sentence that states the availability of copper should not be thought of as limited.

Now, the question wants a statement that can oppose the argument. Option B is the only answer that suggests that Transmutation is expensive. If transmutation is very expensive, then people are left with current resources of copper which are limited. Option B is correct.

People who got this question right are the ones that recognized that the first sentence of the paragraph is the argument.

Fixed. Thank you

The argument of the essay is copper can be created from other metals and its quantity can not be calculated accurately.
The counterargument must be copper can not be created from other metals and its quantity can be calculated accurately.
According to option A, copper can not be deposited after 50 years of supply from the earth. But it doesn't counter the argument of the passage as it will be possible to get copper from other metals after the time of 50 years.
Option B is correct because if the mentioned process is expensive copper can not be created from other metals and its quantity can be calculated accurately.
Option C is incorrect because it suggests a supplement of copper.
Option D is incorrect as it says deposition of copper is impossible if copper is present in the moon which makes no sense.
Option E is incorrect as it says the calculation of existing copper found from the earth is accurate which does not counterargument the passage.
So the correct option is option B.