— The classroom iscleanit was yesterday.— Sorry I forgot to clean it.A. as; asB. so; asC.

问题补充：

— The classroom iscleanit 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：根据句意教师忘记打扫应该是不如以前干净，故只能选表示不及的意思，not so

……as可以表示此意，故选C。