Which of the following characteristic distinguish arthropoda from annelids and molluscs ?

A. An external skeleton made of chitin (a polysaccharide) and protein rather than a shell made chiefly of mineral salts.

B. Subdivision of the legs into movable segments.

C. Distinct group of muscles, derived from many body segments, that move the separate parts of the exoskeleton.

D. All of the above

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