Frank asked his father a new bike for him and his father said OK.A. buyB. to buyC. buying

问题补充：

Frank asked his father a new bike for him and his father said OK.

A. buy

B. to buy

C. buying

D. bought

答案：

A. buy

(答案→)B. to buy

C. buying

D. bought

解析：句意：弗朗克叫他的爸爸给他买一辆新自行车，他的爸爸说可以。ask sb to do sth要求某人做某事，固定句型，故选B