This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Physiology
Following occurs in living cells only- 
Select and explain. 
A. Simple diffusion, B. Facilitated diffusion, C. Osmosis, D. Active transport
D: Active transport
Answer: D: Active transport 
Explanation: Ans. is 'd' i.e., Active transport "Because the formation and breakdown of ATP require cell activity, active transport mechanisms occur through living membranes."* Active transport require energy (ATP). Energy is produced in living cells. Therefore, active transport is possible only in living cells.