Your guess is as good as mine.

我跟你一样拿不准。

----------------------------------------------------------------------
1. I've nothing to say about the decision.我对这个决议没什么可说的。

2. I really don't know what to say. 我确实没有什么主张。

3. I couldn't say, I'm afraid.恐怕我说不上来。

4. It makes no odds to me.这对我无所谓。