in a short moment, people suddenly didn’t know how to answer sb’s question.
- renpeng December 2012
Most of your examples are ok. Let me add a few for you:
1. Let me get back to you.
2. Not sure.
3. Who knows?
4. I'll look into it.
5. Let me think about it a bit.
And, doubtless, many (many) more. You'll find that English is VERY FLEXIBLE when it comes to the numerous ways in which a simple idea can be expressed.