(1) Fairy tales are borrowed the most, and history books are borrowed the least;

(2) The library should get a batch of new books and more fairy tales;

(3)( 105+ 156+ 13 1+ 120)÷4

=5 12÷4,

= 128 (Ben),

A: On average, each kind of books is borrowed 128.

So the answers are: (1) fairy tales, history and (2) fairy tales.