Hi there.
A prime number is a number that cannot be divided into a smaller whole number aside from 1 and itself. An example would be 3; it cannot be divided into a smaller whole number unless it was divided by itself.
Let's look at the factors of 63:
1 * 63
3 * 21
7 * 9
On the left side of our multiplication table above, we have the list of prime numbers (1, 3, and 7). To the right, we don't (63, 21, and 9).
From our answer choices, we have B.) 7 included, so that is your answer.
To debunk the right side of the table:
63 can be divided into smaller numbers, which are listed above.
21 can be divided into 3 and 7.
9 can be divided into 3 and 3.
I hope this helps!
