I believe it's B. Cytoskeleton and Cytoplasm.
The answer is: <span>larger horses have longer legs.
</span>The ancestors of horses lived in the forest, where they could hide from the predators. But, with the first steppes, they could be spotted by the predators. Horses had to adapt in order to survive. Thus, their legs became longer through time so horses could run faster to escape predators.<span>
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<span>Your answer would be inadequate sunlight.</span>
