Look! The children in the river.A. swimB. are swimmingC. is swimmingD. swims

问题补充：

Look! The children in the river.

A. swim

B. are swimming

C. is swimming

D. swims

答案：

A. swim

(答案→)B. are swimming

C. is swimming

D. swims

解析：句意：看！这个孩子正在河里游泳。句中有Look表示现在正在进行的动作，故用现在进行时态，故选B