In winter we must pay attention to .A. keep warmB. keep warmlyC. keeping warmD. keeping w

问题补充：

In winter, we must pay attention to .

A. keep warm

B. keep warmly

C. keeping warm

D. keeping warmly

答案：

A. keep warm

B. keep warmly

(答案→)C. keeping warm

D. keeping warmly

解析：to在这句话里当介词用，所以后面要用动名词，keep后接形容词表示保持怎么样，接副词表示怎样地保持，根据题意，这里应是保暖，所以选C。