What does it mean to say that something fluctuates?
a. it expands
b. it is imported
c. its number rises and falls
d. it has risen above. sea level

Which evidence is most likely used to indicate the beginning of solar system formation? a. materials combined to form a mass. b. materials were pulled together by gravity. c. water condensed and collected to form oceans. d. different species of microorganisms lived on earth.

Which of the following best describes brazil's economy from 1650-1880? a. it gradually shifted to manufacturing as the industrial revolution progressed. b. it was based on mining. c. it was based on plantation agriculture, where slaves served as a labor force. d. it was based on small, family-owned farms.

The action of eventually a low island to form. a. wind b. waves c. volcanoes d. tectonic plates