Help with my daughter's study guide? earth science..?

[Jennifer]

As part of the carbon/oxygen cycle, which process would remove carbon dioxide from the atmosphere?
a. the growing of rain forests
b. burning gasoline in automobiles
c. burning coal in power plants
d. respiration of animals
e. destruction of the ozone layer
The main source of "greenhouse" gasses is..
a. the rain forests
b. aerosol cans
c. burning of fossil fuels
d. methane from rice paddies
e. man-made fertilizers
The reaction of chemical pollutants with one another in sunlight produces
a. acid rain
b. global warming
c. less pollution
d. greenhouse gasses
e. photochemical smog
What would happen to the nitrogen cycle if all the denitrifying bacteria were destroyed?
a. the cycle would be sped up
b. the cycle would adjust to compensate for the loss of the bacteria
c. chemical reactions would replace the bacteria
d. the cycle would eventually stop
e. the cycle would keep right on going