—What made him so worried.—his wallet.A. Having lostB. LosingC. LoseD. Lost

问题补充：

—What made him so worried.

—his wallet.

A. Having lost

B. Losing

C. Lose

D. Lost

答案：

A. Having lost

(答案→)B. Losing

C. Lose

D. Lost

解析：考查动名词短语做主语。本句使用losing his wallet作为句中的主语。ACD三项不能在句中做主语。句意：—什么事情让他如此担忧？—丢了钱包。故B正确。