She is newcomer to chemistry but she has already made some important discoveries.A. the;

问题补充：

She is newcomer to chemistry but she has already made some important discoveries.

A. the; the

B. the; /

C. a; /

D. a; the

答案：

A. the; the

B. the; /

(答案→)C. a; /

D. a; the

解析：考查冠词：第一空是泛指：一个新来的人，第二空不填，因为chemistry是学科，前面不加冠词。句意：她是刚刚学习化学的，但她已经有一些重要发现了。选Ｃ。