这是我这辈子听过最愚蠢的主意。

This is the ___dumbest idea I've ever heard in my life.

看到大火突然烧起来，他吓得说不出话来。

He stood ___dumbfounded when he saw the fire suddenly break out.

别装傻了，我们都知道你明白这个规则。

Stop acting ___dumb, we all know you understand the rules.