Final answer:
Cellulose is the molecule that makes the trunk of a tree sturdy.
Step-by-step explanation:
The molecule that makes the trunk of a tree sturdy is cellulose. Cellulose is a complex carbohydrate made up of a long chain of glucose molecules. It provides structural support to plants and is a major component of the cell wall in plant cells. Due to its strong and rigid nature, cellulose helps to maintain the shape and stability of the tree trunk.
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