The appropriate answer is C. Trees. Trees remove carbon dioxide from the atmosphere through the process of photosynthesis. The carbon dioxide is used along with water and energy from the sun to make food for plants.
Corals extract dissolved carbon dioxide from the ocean to secrete their hard rocky structures.
Crab shells and other marine animals with shells have their bodies incorporated into the seafloor when they die. The sea floor eventually gets subducted where it melts. The carbon present here gets back into the atmosphere via volcanic eruptions.