Nobody knew who was the first at school that morning when the window was broken.A. arrivi

问题补充：

Nobody knew who was the first at school that morning when the window was broken.

A. arriving

B. arrived

C. to arrive

D. have arrived

答案：

A. arriving

B. arrived

(答案→)C. to arrive

D. have arrived

解析：句意：当窗户被打碎时，那天早晨没有人知道是谁第一个到达学校。不定式做补足语表示具体的将要进行的动作，结合语境可知本句不缺少谓语动词，故选C。