The passage assumes that Standard sheets of printer paper carry almost the same amount of wood pulp. Twenty-five percent of the wood pulp contained in a sheet of (Class B) paper was recycled from used sheets of (Class A) paper.
The conclusion followed is based on:
A: Class B sheets of paper cannot be recycled further. (the author do not explain further the recycling of Class B paper, so assuming this will be a speculation, moreover it has nothing to do with the recycling assumption) (Irrelevant)
B: Unrecycled wood pulp is of better quality than recycled wood pulp. (We can't speculate this, paper quality of standard sheets are not mentioned) (incorrect)
C: When a sheet of standard printer paper is a recycled, all of its wood pulp is recovered. (This might be the hypothesis followed in the passage. maybe that's they are using paper of class A to recycle as Class B) (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. (NO quantitative measure of number is given to determine such) (Incorrect)
E: All of the paper in Class A had been made from recycled wood pulp. (No paper making process of Class A paper is explained in the passage) (Irrelevant)
Answer is C
_________________