This teacher was a dutiful son.

这位老师非常的孝顺。

Firstly, he must be a dutiful son.

首先，他必须是一位孝子。

He's the dutiful son.

他是个孝顺的儿子。

You're playing the part of the dutiful son.

你在扮演一个孝顺儿子的角色。

You're playing the part of the dutiful son.

你在演一个听话的儿子的角色。