下列句子中加横线的成语使用恰当的一句是（ ）

Could you tell me what he said just now — Sorry, I_____ what was happening outside.

Studies indicate that people are more _______ to suffer from back problems if they sit before computer screens for long hours.

We firmly believe that war never settles anything. It only _____ violence.

In my opinion, he is a(n) _____ person, that is, he says exactly what he thinks. [ ]