21. How much of Earth's mass is water?
A Less than 1 percent.
Correct! The water is concentrated at the Earth's surface, so
the relative mass of all Earth's water compared to the whole planet is small— only about 0.02 percent.
B About 72 percent
Nope.
C About 74 percent
Nope.
D About 78 percent
Nope.
E Over 90 percent
Incorrect
