While he was investigating ways to improve the telephone,Newton made ________ discovery which comple

While he was investigating ways to improve the telephone,Newton made ________ discovery which completely changed ________ man's understanding of color．

A.a;/

B.a;the

C./;the

D.the;a

答案及解析： A

解析：

discovery发现，前加不定冠词表泛指；

第二空后man一词的单数形式且前无冠词，意为“人类”。