Question 1
Sources of natural variable gases and materials include all of the following
except◦ volcanoes.
◦ forest fires.
◦ plants and decaying plants.
◦ industrial activity.
Question 2
Stars give off electromagnetic radiation because
◦ matter is converted into energy.
◦ matter and energy totally annihilate one another in matter-antimatter reactions.
◦ energy is converted into matter.
◦ kinetic energy is converted into potential energy.