A fifteen-foot tree growing in a fence row is used as a fence post, to which barbed wire is stapled at a height of five feet. Years later, the tree is thirty feet high. The fence is .

The fence will still be five feet high because the lengthening of the tree occurs at the apical meristem

Step-by-step explanation:

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years later after the tree is now thirty feet high,  The barbed wire has been initially stapled at a height of five feet.

However a tree increases from its apical meristem therefore the barbed wire fence will still remain at that same height of five feet high.

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