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) same
B) investigating the effects that changes in working conditions would have on workers' performance
c) that investigated changes in working conditions' effects on worker's performance.

Answer is B
IMO the answer should be c

please explain. I feel that c flows better