[SC悬赏令] # 求助SC 700-800 IDIOMS 第9题

During the twentieth century, the study of the large-scale structure of the universe evolved from the theoretical to the practical; the field of physical cosmology was made possible because of both Einstein's theory of relativity and the better ability to observe extremely distant astronomical objects.  

A  because of both Einstein's theory of relativity and

B  by both Einstein's theory of relativity and

C  by Einstein's theory of relativity and also

D because of Einstein's theory of relativity and also

E as a result of both Einstein's theory of relativity and

OA是B

想请问一下这里的C哪里错了呢？

刚开始以为是and also加一个also 冗余

答案解释是：The construction "by... and also" requires the idiom "by X and also by Y."

为什么不能是 by (Einstein's theory of relativity and also the better ability to observe extremely distant astronomical objects) 呢？

以及关于and also搜了一下，ron说并不是redundant

"you may not ever have seen "and also" in a correct SC answer, but there are certainly situations in which it is acceptable.