Which one is more natural to say?
I'm interested to know which one of those answers is sounded more naturally:
For example I am being asked: " What do you think about it? " and I want to answer:
1. I'd rather stay silent
2. I'd rather be staying silent
3. I'd rather be silent
4. I'd rather keep silence
5. I'd rather be keeping silence.
Maybe other your options?
Thank you in advance for your help.

Question

Which one is more natural to say?
I'm interested to know which one of those answers is sounded more naturally:
 For example I am being asked: " What do you think about it? " and I want to answer:
1. I'd rather stay silent
2. I'd rather be staying silent
3. I'd rather be silent
4. I'd rather keep silence
5. I'd rather be keeping silence. 
Maybe other your options?
Thank you in advance for your help.

Answer

1. I'd rather stay silent  > ok
2. I'd rather be staying silent  > x
3. I'd rather be silent > ok
4. I'd rather keep my silence >ok
5. I'd rather be keeping silence. >X
My choice > I would rather not comment.