Which process acts to remove carbon dioxide from the atmosphere?
a. Lightning
b. deforestation
c. photosynthesis
d. burning fossil fuels
e. volcanic eruptions
Question 2Since 1958, CO2 in the atmosphere has
a. increased in concentration by 30.
b. decreased in concentration by 30.
c. remained at about the same concentration from year to year.
d. disappeared entirely.
e. has doubled in concentration.
Question 3The most abundant greenhouse gas in Earth's current atmosphere is
a. carbon dioxide (CO2).
b. nitrous oxide (N2O).
c. water vapor (H2O).
d. methane (CH4).
e. chlorofluorocarbons (CFCs).
Question 4The only substance near Earth's surface that is found naturally in the current atmosphere as a solid, liquid, and a gas is
a. carbon dioxide.
b. water.
c. molecular oxygen.
d. ozone.
e. carbon.
Question 5Typically, 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 6Water 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.
Question 7Which of the following is considered a variable gas in Earth's atmosphere?
a. water vapor
b. nitrogen
c. oxygen
d. argon
e. helium
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