--The classroom is clean it was yesterday.Sorry I forgot to clean it.A. as; asB. so;

问题补充：

--The classroom is clean it was yesterday.

--Sorry, I forgot to clean it.

A. as; as

B. so; as

C. not so; as

D. more; than

答案：

A. as; as

B. so; as

(答案→)C. not so; as

D. more; than

解析：句意：教室不如昨天干净，对不起，我忘记打扫了。not so(as)…as…,不如，是同级比较的否定，故选C。