1.C动词不定式做定语,至于你讲的两者间没啥区别,就是前者限定了物,而后者没任何限定,就像 I don't know what to buy. I don't know which pen to buy .是一样的.2.C 根据你的补充问题,我对答案简单讲一下你就理解....（）good time they are having now! ()great fun it is !A what ,what aB what a ,what Chow ,whatD how a , what a .要讲解为什么答案是B，那时间time是不可数的呀，为什么用了what a ？你好！不好意思，今天太忙了！time: 单数名词(相当长的)一段时间(前面可加a,但无复数情况）如：He stayed for quite a time...他呆了相当长的一段时间。After a time they came to a pond.过了好久，他们来到一个池塘。故在感叹句中有a.