I don't understand the instructions.

　　我不懂這些指令的意思。

　　I don't understand what you are talking about

　　我不明白你在說(shuō)什么。

　　'I don't understand,' the Inspector mumbled, passing a hand through his hair

　　“我不明白，”巡官一邊嘟囔道，一邊用手捋了一下頭發(fā)。

　　I don't understand how the two facts relate.

　　我不明白這兩個(gè)事實(shí)有什么聯(lián)系。

　　I don't understand what you're talking about.

　　我不懂你在說(shuō)什么。