It is A. for acquiring energy
Giraffes have long necks so that they can reach tree leaves. Technically their long necks help them contain the energy from the leaves by reaching them. that's why the answer is A.
It's not B because reproducing is like a giraffe giving off energy also meaning having little giraffe babies.
it's not C because maintaining the giraffe's structure is basically to stay or try to stay the same as it was before. it is also not specifically about the neck it is talking about the giraffe in generally.
It's not D, although giraffes use their necks to fight off other giraffes protecting has nothing to do with using their necks to eat leaves. they don't have to protect the leaves and the leaves aren't really in any harm so protecting themselves of the leafs has nothing to do with what the question is asking.
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