be careful when crossing the street! A. MustB. ShouldC. Ought toD. Do

问题补充：

be careful when crossing the street!

A. Must

B. Should

C. Ought to

D. Do

答案：

A. Must

B. Should

C. Ought to

(答案→)D. Do

解析：可联系答.案.网客服索取。