(A) A small quantity of lignins are currently sold by paper manufacturers to chemical companies, but most of the lignins produced are burnt as waste. - It does not weaken the argument that the companies should invest into paper manufacturers.

(B) The 20-dollar-a-barrel oil price as a threshold of profitability for using lignins allows for the increased cost of refining crude oil that has been extracted using lignins. - Out of scope.

(C) Only one-half to two-thirds of the total oil in a well can be extracted using conventional techniques of pumping and flooding with water. - Not relevant to the argument.

(D) Petroleum-based substances that can be used as a substitute for lignins in extracting oil are costly and are made from oil, and these substances therefore increase in price as oil increases in price. - This strengthens the argument.

(E) The quantity of lignins produced annually in the manufacture of paper is several times larger than the amount that is likely to be useful in the oil industry. - Yes. Only a portion will be used by chemical companies and hence it is not wise to invest in paper manufacturers.

Answer E