everyone is much quieter than usual when taking a test为什么用taking?
问题描述：
everyone is much quieter than usual when taking a test为什么用taking?
答
这是从属连词+ 分词 作状语的结构
= when ( they are ) taking a test
再如：
Be careful while crossing the road.
不懂追问*^__^* 什么是从属连词？力求简洁正确引导状语从句的连词都叫从属连词