Water, oxygen and carbon dioxide can enter a cell through: A. Simple diffusion B. Osmosis C. Facilitated diffusion D. Active transport

Water, oxygen, and carbon dioxide can enter a cell through various methods, but the specific process that allows these substances to move across the cell membrane includes:

A. Simple diffusion: This process involves the movement of molecules from an area of higher concentration to an area of lower concentration without the use of energy. Small non-polar molecules like oxygen and carbon dioxide can diffuse directly through the lipid bilayer of the cell membrane. Water molecules also move through the cell membrane by a specialized form of diffusion called osmosis, which is a type of simple diffusion specific to water.

Facilitated diffusion (C) also aids in the movement of certain molecules across the membrane, but it usually involves specific carrier proteins that assist in the transport of larger or charged molecules. Active transport (D) requires energy and typically moves molecules against their concentration gradient, requiring specialized proteins (like pumps) to transport substances into or out of the cell.