我父亲是个严肃的人，很少讲笑话。

My father is a ___serious man who rarely tells jokes.

经理看起来很严肃，但他实际上很平易近人。

The manager appears ___serious, but he's actually quite approachable.

他太严肃了，欣赏不了无厘头的喜剧。

He's too ___serious to enjoy silly comedies.