D. Produces vitamin D.
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Why it’s not A:
The skeleton does provide shape and support, if not we wouldn’t be able to walk, we would stumble down, like a flop •.•.
Why it’s not B:
If we didn’t have the skeleton, we wouldn’t be able to move.
Why it’s not C:
Each part of the skeleton protects the organs, for ex: the skull protects the brain.
Why it’s D:
The skeleton doesn’t provide vitamin D. The skin can, through the sunlight.