The answer is C. plants pull in CO2 and release oxygen
1. natural selection acts on existing traits because you can not evolve into something you didn't have
2. original structures evolve to accomplish new function in order to survive
True. Greenhouse gases are composed of many molecular components that provide and are necessary for life to still exist on earth. For example, the carbon dioxide and the others alike. However, when these exceed the necessary level and amount in the atmosphere, they cause tremendous increase in temperature.