#### Answer

A.

#### Work Step by Step

In order to find the prime factorization of 100, we can try to divide 100 by the first prime, 2.
$100\div2=50$
Try to divide 50 by 2.
$50\div2=25$
25 cannot be divided by 2 or 3, so we divide 25 by the next prime number, 5.
$25\div5=5$
5 itself is a prime number, so we cannot simplify any more. The prime factorization of 100 is $2\times2\times5\times5=2^{2}\times5^{2}$.