I think it's (ASTRONOMICAL UNIT)
Explanation:
It is used to compare the distances of other bodies in the Solar System, such as the Sun, the planets, comets, and asteroids.
When the balloon is kept in the sun, due to Sun's heat, the kinetic energy of gaseous particles inside the balloons also gets increased and the balloon expands. This will increase the pressure on the walls of the balloon. It continues to expand and comes to a stage when the baloon bursts.
Even though all materials are at the same temperature when they come out of the dryer, some like the zipper are far better conductors of heat and can burn you. Cloth is not a good conductor of heat.