This is book. And it is English book. A. a aB. an an C. a an D. an a

问题补充：

This is book. And it is English book.

A. a, a

B. an, an

C. a, an

D. an, a

答案：

A. a, a

B. an, an

(答案→)C. a, an

D. an, a

解析：a 用在辅音音素前面；an用在元音因素前面. 句意:这是一本书。它是一本英语书。结合语境可知选C。