Answer:
You increase its density.
Step-by-step explanation:
Think of what happens when you squeeze a balloon.
A is wrong, because the volume decreases. The balloon gets smaller.
B is wrong. The temperature of the balloon does not change.
C is correct. You increase the density of the gas. Density = mass/volume. You have the same mass of gas in a smaller volume, so its density increases.
D is wrong. The more you compress the balloon, the more difficult it becomes. The pressure increases.
