我的语法也不算差了,楞是被prep 157搞糊涂了

157.
        In the mod-1920s 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 one workers’ performance

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

D.    that investigated changes in working conditions’ effects on workers’ performance

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

A: their没有指代

B: correct

C: that没有指代

D: conditions’ effects 改变原意

E: changes in working conditions would have做定语修饰the effects，what the effects没有谓语。

B怎么对了? effects复数,怎么能够跟单数动词changes? 莫非changes在这里是名词?

B的答案印错了，changes in working conditions would have ON workers' performance

changes是名词，工作条件的变化对工人表现的影响

sign

I'm really confused with "one" in B

So if it is print error, B is the best answer