I think the answer would be
A) to transport water and food
Warm air rises, expands, then cools. As cool air sinks it may cause precipitation. Some air masses such as the MT which originate in warm environments carry humid air and cause heavy precipitation in some areas.
Answer:
The Carbon Cycle
Carbon moves from the atmosphere to plants.
Carbon moves from plants to animals.
Carbon moves from plants and animals to soils.
Carbon moves from living things to the atmosphere.
Carbon moves from fossil fuels to the atmosphere when fuels are burned.
Carbon moves from the atmosphere to the oceans.
Hope This Helps