介词加关系代词的复杂用法， 就是many of which 怎么用

不懂， the instruments by means of which the temperature is measured is called .....
they asked a lot of questions , many of which i don't know...
这种怎么用？什么时候该用，怎么用法

the instruments by means of which the temperature is measured is called....
the instruments is called是句子的主干
by means of which the temperature is measured =which the temperature is measure by means of (是定语从句部分，which指the instruments, which作了by means of 的宾语）
they asked a lot of questions , many of which i don't know...
many of which i don't know是非限制性定语从句，know的宾语是many of which , which指questions)
又如： I have two sisters, both of whom are dancers
both of whom are dancers是非限制性定语从句， WHOM 指sisters
There was no room in which they could live.
in which ( in which = where)they could live.是定语从句，=which they could live in
which 指room
关键是你要弄明白which指什么！

分成两个句子 They asked a lot of questions. Many of them I don't know. 改成定语从句，只要把句号改成逗号， them 改成which或whom eg. I have many books. Some of them are interesting. 变成 I have many books, some of which are interesting. He has many frineds. One of them is from China. 变成 He has many friends, one of whom is from China. 希望对你有用！