Standard sheets of printer paper do not vary in the amount of wood pulp that they contain. Twenty-five percent of the wood pulp contained in a certain class of sheets of standard printer paper (Class B) was recycled from used sheets of standard printer paper of a different class (Class A). Since all Class A sheets were recycled into Class B sheets and since the amount of material other than wood pulp in a sheet of standard printer paper is negligible, it follows that Class B contains 4 times as many sheets of paper as Class A.
The conclusion of the argument follows logically if which one of the following is assumed?
Before looking into answer choices, lets examine the para above. It says that Class A is a standard sheet of printer paper and these papers do not vary in the amount of pulp they contain. This is recycled to create Class B papers which have 25% of recycled wood pulp.
Conclusion : Class B has 4 times as many sheets than A
Only possibility if A had 100% pulp and out of which 25% * 4 are used to create 4 Class B papers
Now any answer choice that talks about 100% of wood pulp in A would be correct.
A: Class B sheets of paper cannot be recycled further. -------- Irrelevant. Does not explain how 4 Class B paper = 1 Class A paper
B: Unrecycled wood pulp is of better quality than recycled wood pulp. -------- Irrelevant. Does not explain how 4 Class B paper = 1 Class A paper
C: When a sheet of standard printer paper is a recycled, all of its wood pulp is recovered. -------- If 100% is not recovered then it will be difficult to make 4 Class B papers. Hence this is correct.
D: The percentage of wood pulp in a sheet of standard printer paper that can be recovered during recycling varies depending on how such paper was used. -------- Irrelevant. If it would vary then the conclusion will not hold hence this cannot be my assumption
E: All of the paper in Class A had been made from recycled wood pulp. -------- Irrelevant. Not the point of the argument.