The books of three people are different from each other, which is a matter of arrangement, or not to put them back. You can think of it this way. Let three students choose five different books by themselves. The first person to choose has five choices. After he took one book, the second man chose among the remaining books. He also takes one, and the third person has only three choices.

So * * * has 5×4×3 different selection methods.

(2) Choose three books from five different books and give them to three students, one for each.

The books of three people can be the same, which is equivalent to the problem of putting them back. There may be several books in five different books, and everyone has five choices, so * * * has five different choices.