It is a good habit to go to bed early and get up early.A. aB. anC. theD. 不填

问题补充：

It is a good habit to go to bed early and get up early.

A. a

B. an

C. the

D. 不填

答案：

A. a

B. an

C. the

(答案→)D. 不填

解析：固定搭配。