Which of the following is a perfect square? a 127 b 100 c 13 d 102

100.

Justification.

A perfect square is a number that can be expressed and the square of an integer.

In this case, 10^2 = 100, so 100 is a perfect square.

It is a good idea to memorize the first perfect squares. I recommend you memorize the squares of the numbers from 1 to 14. That will help you a lot in some standardized tests,which requires to answer some quesitons fast:

100 = 10 * 10 = 10^2