He was astonished at what he found.请问这句话是什么从句,先行词是什么?

问题描述:

He was astonished at what he found.请问这句话是什么从句,先行词是什么?

He was astonished at (what he found)
宾语从句,做介词后面的宾语,是个从句
只有定语从句有先行词