【正确答案】 C

【答案解析】[分析] 本题测试语法结构的用法。在被动语态中， hear，make，see，have等动词后，动词不定式作主补，动词不定式符号to不能省略，故选C项。而在主动语态中这类动词后动词不定式作宾补，动词不定式的符号to通常省略。例： The workers were made to work twelve hours a day． I often saw him play football with his classmates．