I have a few questions about the demonstrative plurals: Bu Şu ve O, more particularly when used with plural nouns.

1)  If i point to a group of objects, say a stack of books, do i say: "Bu ne(dir)?" or "Bunlar ne(dir)?"  (What are these?)

2) What is the appropriate response to that question?

"Bunlar kitaplar." or "Bu kitaplar." or "Bunlar kitap." (These are Books)

[I see different grammar articles telling me to say different things.] 

3) If I am responding with a specific quanity. Would it be: "Bu iki kitap." or "Bunlar iki kitap." ?  

4) Is there a difference between saying: "These books..." and "These are books"?

Is I was to say, "I read these books.", is "Bu kitaplar okudum." correct?

If does "Bu Kitaplar" mean "these are books". Or would i need to say "Bunlar Kitaplar"?

I am not sure if that makes sense. I just am a bit unsure about this, and i saw a few coflicting comments online. (One saying Bunlar kitaplar is incorrect, one saying to use Bunlar kitaplar.)

Thank you for your help!

1. I think you could say either. But ´what are these´ is literally Bunlar ne(dir)?

2. I have seen both Bunlar kitaplar and Bunlar kitap, not sure which is better.

3. Bu iki kitap, I think Bunlar iki kitap is wrong.

4. For ´I read these books´, I think: Bunlar kitaplar is wrong, bu kitaplar is correct