While he was investigating ways to improve the telescope, Newton made _______ discovery which completely changed _______ man’s understanding of colour.
A.a;/
B.a;the
C./;the
D.the;a
A
discovery在表达“所发现的事物” 时是一个可数名词,由于没有说明这是什么样的发现,所以用不定冠词;man单独使用表“人类”,前面不加冠词。