补充66

66. In the mid-1920’s the Hawthorne Works of the Western Electric Company was the scene of an intensive series of experiments that would investigate changes in working conditions as to their effects on workers’ performance.

(A) that would investigate changes in working conditions as to their effects on workers’ performance

(B) investigating the effects that changes in working conditions would have on workers’ performance

(C) for investigating what are the effects in workers’ performance that changes in working conditions would cause

(D) that investigated changes in working conditions’ effects on workers’ performance（B）

(E) to investigate what the effects changes in working conditions would have on workers’ performance

After readng the discussions, I still have not clear idea about the differences between B and D.

What is (are) error(s) in the choice D? Many thanks for reply.