credulous

他太轻信了，居然相信了那个明显是骗局的投资项目。

He was so ___credulous that he believed the obviously fraudulent investment scheme.

那些轻信的游客把钱交给了一个承诺带他们私密游览的陌生人。

The ___credulous tourists handed over their money to a stranger who promised them a private tour.

即便是最容易轻信的观众，也难以接受这位魔术师最新的说法。

Even the most ___credulous spectator would find it hard to accept the magician's latest claim.