If you fill up a balloon with a small amount of air, then set it in direct sunlight, you will see that the balloon expands. This expansion is due to an increase in volume, which results from
A) a decrease in the pressure of the air in the balloon.
B) an increase in the temperature of the air in the balloon.
C) an decrease in the pressure of the air outside of balloon.
D) an increase in the temperature of the rubber that makes the balloon.