writer she is excellent teacher she is not very good.A. As; but asB. As; and asC. As a

问题补充：

writer, she is excellent, teacher she is not very good.

A. As; but as

B. As; and as

C. As a ; but as a

D. As a; and as a

答案：

A. As; but as

B. As; and as

(答案→)C. As a ; but as a

D. As a; and as a

解析：作为一个作家，她是优秀的；但作为一名教师，她就不是很好的了。 writer 和teacher都是可数名词，单数要加冠词a。