I was wondering if it was possible to borrow more than two books?

[it-is-niaz]

1. At a library: I was wondering if it was possible to borrow more than two books?
2. At a library: I was wondering if it would be possible to borrow more than two books?
3. At a library: I was wondering if it could be possible to borrow more than two books?
4. At a library: I was wondering if it is possible to borrow more than two books?

May I ask which sentence is correct?

 

[GoesStation]

They're all possible. Number two sounds the least unnatural to me.

Do you know how a native speaker would be likely to ask this?

 

[Raymott]

Do you know how a native speaker would be likely to ask this?

I'd say 1.
I'm not sure how a native speaker would be more likely to ask his. "Can I borrow more than two books?" Not sure what you have in mind.

 

[it-is-niaz]

Do you know how a native speaker would be likely to ask this?

I'll go for the same response that Raymott gives.
what is the use of "I was wondering"? When native speakers use that?

 

[Raymott]

It's just a politeness thing.

Librarian: "Can I help you?"
1: "Yes, can I borrow more than two books?"
2: "Yes, I need to borrow more than two books."
3: "Yes. Is it possible to borrow more than two books?"
4: "Yes, I was wondering if I could borrow more than two books." (or other similar sentence).

These are all possible.
1. is saying what you want. 2. sounds a bit abrupt - especially if you don't know whether it's possible. 3. is fine.
It's true that 4 uses more words, but that's OK. It's a bit like saying "I would like ..." rather than "I want ...".

You could also look at the first two answers here (13 and 16):
https://english.stackexchange.com/q...ing-if-there-are-synonyms-for-i-was-wondering

 

[Tdol]

#3 is the one I'd be least likely to use.