—_____.

A. Because she lost her wallet B. she lost her wallet

C. Losing her wallet D. To lose her wallet

【答案】C

【解析】考查句子成分。句意：什么让她不高兴。丢了钱包。根据 What made her unhappy可知这个句子缺少主语，动名词可以做句子的主语，故选C项。