15. satellites remain in orbit around earth because
a. the moon's gravitational pull on them is equal
to earth's pull.
b. no forces act on them.
c. their motors keep them moving in circles.
d. the curve of their paths as they fall matches
the curve of earth.

What is one affect on the australian environment due to the introduction of non-native european rabbits? (a) more grass grew in response to the need of the growing population of rabbits. (b) the rabbits balance out the food chain as they became a natural prey to many predators. (c) the rabbits the land by digging, which caused the soil to spread much needed nutrients. (d) the rabbits out-competed other small animals species and caused them to go extinct.