kinds是什么意思啊

　　These kinds of questions often appear in the exam.

　　这几类问题在考试中经常出现。

　　Human beings are genetically programmed to learn certain kinds of language.

　　人类生来有学习某几种语言的遗传因素。

　　I like all kinds of music from opera to reggae.

　　我喜欢各种音乐，从歌剧到雷盖都喜欢。

　　In crude terms, the causes of mental illness seem to be of three main kinds.

　　简略地说，导致精神病的原因看起来主要有三种。