D. Fossil fuels are the remnants of organisms that lived a long time ago and were buried, heated, and formed into hydrocarbons.
C. The cell took in another ancient prokaryotic cell, which began living inside it.
Deep water currents affect the number of organisms found in the area by circulating nutrients due to upwelling. Upwelling is a process where cold water surfaces and encourages nutrients to the surface. When exposed to sunlight, they initiate energy which keeps the flow of the ecosystem.