Can someone help me understand
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Keyword in all that is "spherical." This tells you that we are using... well... a sphere. This also means we are looking for volume. If it helps, I would underline this word.
The formula for the volume of a sphere is V = (4/3)(pi)(radius)³
So, plug in your given information, the radius.
V = (4/3)(pi)(4)³
V = (4/3)(pi)(64)
V = (256/3)(pi)
Option D is your answer.