A：Do you have a minute?

你现在有空吗?

B：Sure. What's up?

有啊，有什么事吗?

注释：

a.free a. 有空的

= available

Are you free now?

= Are you available now?

= Are you off now?

(你现在有空吗?)

b.I think so.我想是吧。

I don't think so.

我想不是吧。/我不这么认为。

A: Is she beautiful?

(甲：她美吗?)

B: No, I don't think so.

(乙：不，我不这么认为。)