问一道题，求高人解答，谢谢。

mingming8152

In a study of the effect of color on productivity，50 of 100 factory workers were moved from their drab workroom to a brightly colored workroom.Both these workers and the 50 who remained in the drab workroom increased their prod-uctivity， probably as a result of the interest taken by researchers in the work of both groups during the study.Which of the following， if true， would cast most doubt upon the author's inter-pretation of the study results given above？

（A） The 50 workers moved to the brightly colored room performed precisely the same manufacturing task as the workers who remained in the drab workroom.

（B） The drab workroom was designed to provide adequate space for at most 65 workers.

（C） The 50 workers who moved to the brightly colored workroom were matched as closely as possible in age and level of training to the 50 workers who remained in the drab work-room.

（D） Nearly all the workers in both groups had volunteered to move to the brightly colored workroom.

（E） Many of the workers who moved to the brightly colored workroom reported that they liked the drab workroom as well as or better than they liked the brightly colored workroom.

正确答案B，我不知道C为什么不对。谢谢

奋斗GMAT中

我个人认为B的结果是另有他因（对生产率提高一定是有好处的），而C年龄和培训水平虽然一致性高，但是并没有说明一致性高对提高生产效率好还是不好（比较而言），而且测试普遍性的规律时相似的分在一组也很正常

我个人的理解一家之言