Typically, water vapor occupies about what percentage of the air's volume near Earth's surface?
a. about 78 percent
b. about 21 percent
c. close to 10 percent
d. less than 4 percent
e. less than 1 percent
Question 2
Water vapor molecules
a. are invisible.
b. color the sky blue.
c. make clouds white.
d. are very small drops of liquid water.
e. can exist in the frozen state.