Final answer:
The diffusion of oxygen at body cells occurs due to a concentration gradient and is a passive process.
Step-by-step explanation:
The true statement about the diffusion of oxygen at body cells is that it occurs due to a concentration gradient. Oxygen moves from an area of higher concentration, such as the bloodstream, to an area of lower concentration, which is the cells that need oxygen for energy production. This process is passive and does not require energy.
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