GRE Reading Comprehension: JiJing 352-GRE阅读机经352篇 - MCN7N7V4YAQ7CO75J

In order to choose between the two hypotheses, it would be most useful to determine which of the following? A. Whether mice sometimes produce IDO when they are not pregnant B. Whether the immune systems of fetal mice are capable of attacking the tissue of the mother C. Whether there are cases in which the immune system of a pregnant mouse rejects some fetuses but not others D. Whether IDO is the only substance capable of suppressing the immune system produced by mice E. Whether the immune systems of pregnant mice that are given a drug that inhibits IDO production subsequently reject the fetus.