第29题: [单项选择]The secretary worked late into the night, ______ a long speech for the president. A. to prepare B. preparing C. prepared D. was preparing 参考答案:B 答案解析:[解析] 在此句中,现在分词"preparing"作伴随状语。A项是不定式,可以做目的状语,但目的状语前不用逗号。C、D项属语法错误。例如:Kelley was busy in the kitchen