[求助]不知哪来的题目再一题~~

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 productivity, 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 dout upon the author’s interpretation 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 I 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 workroom.

（D）Nearly all the workers in both group 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.

The key is “B”…WHY?

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

B is correct b/c  the workers' higher productivity was due to the larger space  available,  but not due to the survey.

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

D is not related b/c voluntering has nothing to do with production.

谢谢mbz

I don't want to type Chinese, because it would take me a lot of time to do so. Here is the English translation:

When employees know that their work is being check by the reserchers, they work harder to improve the production.

Thanks....mbz

I got it~~