Hello!
The answer is:

Why?
Let's explain with an example the definition of a multiple.
Multiple of the number 1 are: 1, 2, 3, 4, 5 and so...
Multiple of the number 3 are: 3, 6, 9, 12, 15 and so...
A multiple of a number is the repeated sum of itself, from the example:
Multiple of the number 1 are: Itself, (1+1), (1+1+1), (1+1+1+1), (1+1+1+1+1) and so...
Therefore,
Multiple of
are:

Have a nice day!