A. Because both have a limited supply of air, water, and other resources.
B. Because the Earth moves around the sun as fast as a spaceship.
C. Because we can travel to outer space.
D. Because the Earth never stops moving.
A. About 80 miles per second.
B. About 70 miles per second.
C. About 18 miles per second.
D. About 17 miles per second.
A. Because the Earth is heavily polluted.
B. Because nature cannot recycle its resources.
C. Because more and more people live on the Earth.
D. Because no more new resources can be added.
A. Nature has changed our environment over the years.
B. We must avoid wasting resources and polluting our environment.
C. Our resources are nearly used up.
D. Trips to other planets will help eliminate pollution.