Which two inner planets have water in the form of ice?
a. mars and earth
b. mercury and mars
c. venus and mercury
d. mercury and earth

[fw.02]sinkholes are often formed as a result of the actions of. a.heat on recharge b.pressure on aquifers c.acid in groundwater d.minerals in hot springs

What evidence does the writer give to support his argument about coral reefs? a) he speaks of the activities of coral polyps. b) he describes the composition of the great barrier reef. c) he emphasizes the ways in which coral reefs are fragile. d) he points out the ways that scientists do research on the reefs.

Which layer surrounds the center of the earth? a: crust b: core c: mantle