We should always keep the classroom and tidy.A. cleaningB. cleanedC. to cleanD. clean

问题补充：

We should always keep the classroom and tidy.

A. cleaning

B. cleaned

C. to clean

D. clean

答案：

A. cleaning

B. cleaned

C. to clean

(答案→)D. clean

解析：句意：我们应该总是保持教室干净整洁。keep+形容词，使------保持某种状态。结合语境可知选D。