「え？本当」って言いたい時、”Really?” だけでは寂しいので、いろいろな言い方を覚えておきましょう。

Are you sure?

Are you sure about it?

Are you certain about it?

Do you think it is true?

Do you think so?

How sure are you?

「間違いないよ」って言いたいときには

Yes, I am certain.

I’m a hundred percent certain …

I’m absolutely sure.

I have no doubt about it.

I’m sure about it.

I don’t think there can be any doubt about ….

Of course.

I’m positive.

I’m quite sure about it.

I’m no doubt about it.

I’m absolutely certain that…

ちょっと自信がない時には

I’m not sure about it.

I doubt it.

I’m not really sure about…

I don’t know for sure…

It’s very unlikely.

I have my own doubts.

I don’t think so.

I don’t believe this is true.

There’s some doubt in my mind that …

I’m not a hundred percent sure.

I don’t know yet.