Question

Which of the following is a perfect square?

Answer 1

The answer is D. 100. I hope this got to you in time.

Answer 2

A perfect square is a number that can be square rooted and have a result of a whole number
$\sqrt{127} =11.3$
$\sqrt{13} =3.6$
$\sqrt{102} =10.1$
$\sqrt{100} =10$

As we see above 10 is the only whole number. 

Final answer: 
D