单选题 Every human being who has ever lived had two parents. Therefore, more people were alive three thousand years ago than are alive now.
The reasoning in the argument is flawed because it

A、 overlooks the number of people in each generation during the last three thousand years who left no descendants
B、 disregards possible effects of disasters such as famines and plagues on human history
C、 overestimates the mathematical effect of repeated doublings on population size
D、 fails to take into account that people now alive have overlapping sets of ancestors
E、 fails to consider that accurate estimation of the number of people alive three thousand years ago might be impossible

【正确答案】 D

【答案解析】[解析] 本题作为GRE国内考题罕见的简单题，阅读简单，思维推理也简单。本题推理中无考虑人们可能有兄弟姐妹，也即(D)中所说的人们有共同的祖先，使得“3000年前比现在人多”的成立性受到质疑，所以(D)正确。