C
A 语法不对
B reply及物动词,后不加不定式
D.answer及物动词,后不加不定式可是答案是B，为什么呀？嗯。我错了。reply是不及物动词，answer是及物动词。请看例句He gave me no chance to reply to his question所以，B对，C错。D的话得改成to answer 就对了再次抱歉