7. In which of the following compounds are both members of the pair polymers of carbohydrates that naturally occur in plants only?

A. Starch and chitin
B. Starch and cellulose
C. Glycogen and cellulose
D. Glycogen and chitin

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Note: The original choices B and D ("Sugar, fatty acid, amino acid" and "Carbon dioxide, amino acid, fatty acid") appear to be misplaced and irrelevant to this question, and thus were removed to maintain the coherence of the question.