Well, first off, you see how all the answers say a fraction, then pi? that means that you don't calculate pi into your answer.
But lets see. The radius is 4. V=(4/3)pi*r^2
V=(4/3)pi*4^2
V=(4/3)pi*16
V=(4/3)*16*pi
V=(4/3)*(16/1)*pi
V=(4*16)/(3*1)*pi
V=64/3*pi
so the answer is (B) 64/3pi units cubed.
