Question

Which type of energy increases when you compress a spring? A) elastic potential energy B) kinetic energy C) radiant energy D) sound energy

Answer 1

A
Elastic potential energy because springs have elasticity

Answer 2

The correct answer is 
A) elastic potential energy

In fact, a spring is a store of elastic potential energy, Its elastic potential energy is given by the following equation:
$U= \frac{1}{2} k x^2$
where
k is the spring constant
x is the elongation/compression of the spring with respect to its equilibrium position.

From the formula, we see that the larger the compression (or elongation) of the spring, the greater is the elastic potential energy stored by it.