Be careful when you the street. The traffic is heavy.A. goB. crossC. acrossD. crossing

问题补充：

Be careful when you the street. The traffic is heavy.

A. go

B. cross

C. across

D. crossing

答案：

A. go

(答案→)B. cross

C. across

D. crossing

解析：go 去；cross动词，穿过；across介词，横穿；crossing非谓语动词，穿过。句意：当你穿过大街时，加小心。交通很拥挤。结合语境可知从句中缺少谓语动词，故选B。