Do you believe him? 你相信他的话吗？

Do you believe it? 你相信吗？

I think it's hard to believe. 我觉得这很难相信。

It's too good to be true. 哪有这等好事？

I don't buy your story. 我才不信你的鬼话呢。

Believe it or not. 信不信由你。

Really? 真的吗？

Are you kidding me? 你在逗我呢吧？

You must be joking. 你一定是在开玩笑。

Are you joking? 你开玩笑吧？

Are you serious? 你是认真的吗？

I doubt it. 我怀疑。

I am doubtful about that 我对此表示怀疑。

Don't expect me to believe this. 别指望我相信这事。

It can't be ture. 不可能是真的。

How is that possible? 那怎么可能呢？

He is a doubting Thomas. 他是个疑心很重的人。

I never take him too seriously. 我从来不把他的话当真。

I feel puzzled. 我感到很茫然。

It's doubtful whether this will work. 我怀疑这会不会起作用。