Question

for diffusion to occur, which condition must be met? a concentration gradient must exist. a hypotonic external environment must exist. a hypertonic external environment must exist. dynamic equilibrium must exist.

Explanation:

Diffusion is the movement of substances from an area of higher concentration to an area of lower concentration. A concentration gradient (difference in concentration) is necessary for this movement to occur. Hypotonic and hypertonic environments relate to osmosis in a more specific context related to cells and water - movement, and dynamic equilibrium is the end - state of diffusion, not a requirement for it to start.

Answer:

A. A concentration gradient must exist.