well, since same volume of salt, that means the amounts are the same
lets test a sample cube
if the volume is 64
cube side legnth is 4 each side
SA=96
a rectangular prism with volume of 64 could be
1 by 1 by 64
SA=2(LW+LH+WH)
SA=2(1+64+64)
SA=2(128)
SA=256
256>96
cube has less surface area
D is teh answer