which kind of musical instrument you can play?

题目

which kind of musical instrument you can play?
为什么不用instruments?"of'是“的”的意思吧?那就要用S啊顺便讲讲kind of什么时候（加）复数

答案

which问的是哪一个,所以要用单数,不能用复数.
kind of 表示总类,是词组一般都是跟单数的,请看以下几个例句;
This kind of dress is only appropriate for casual affairs.
这种服装只适合休闲场合.
This kind of animal is in danger of becoming extinct.
这种动物有灭绝的危险.