You're exactly right.

You can be sure.

You can be assured.

I have no doubt about it.

There is no room for doubt about it.

I am not positive.

I am not certain.

Your answer is to the point.

That's a very straightforward answer.

Why not?

No reason not to.

No problem.

Doubtless!

Without doubt!

There can't be any doubt about that.

There is no doubt about it.

You said it.

Your opinion is reasonable.

Your opinion stands to reason.

That's a reasonable opinion.

It's obvious that he won't come back.

It's certain that he won't come back.

He is sure to come tonight.

Surely he will arrive tonight.

No doubt he will arrive tonight.

Sure enough that he will come tonight.

As far as I know.

As far as I can tell.

To the best of my knowledge.

I think so.

That's not right.

That's not correct.

That's not true.

Your idea is wrong.

Your idea lacks morals.

That's not what I mean.

I didn't mean that.

You misunderstood me.

No way!

Never!

Definitely not!

Absolutely not!

It's hard to say.

That's hard to tell.

I can't make up my mind.

I can't decide.

I am in two minds about it.

How can that be?

How can't it be true?

How could that be?

I don't have the slightest idea.

No idea.

I don't know.

It's not my implication.

What I'm saying is another matter.

That's not what I am thinking.

I am not talking about that.