afraid behind Bill studied even harder than ever before.A. To be； of fallingB. Being；

问题补充：

afraid behind, Bill studied even harder than ever before.

A. To be； of falling

B. Being； fall

C. Being； of falling

D. To be； to fall

答案：

A. To be； of falling

B. Being； fall

(答案→)C. Being； of falling

D. To be； to fall

解析：be afraid of表示“害怕某种情况会发生”。