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

The answer is A. a concentration gradient must exist.

Diffusion is the movement of particles down their concentration gradient (from place with high concentration to place with low concentration).

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For diffusion to occur, concentration gradient must exist.

Explanation:

Diffusion is the movement of particles from higher concentration to lower concentration. Since the particles move along the concentration gradient there is no need of energy in the form of ATP. Diffusion is very important process with in our body for the movement of several nutrients and ions. In contrast to this is the active transport where particles move against the concentration gradient that is from low concentration to higher concentration. Such transport requires energy in the form of ATP and hence is called active process. There is one more process called facilitated diffusion where the movement of one particle is dependent or facilitated by other molecule.

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the answer is c. altitude. hope this ! #brainiac