Question 657717
Lets say the original pool is l*w*h.
New pool is 2l*2w*h

a) the SA of bottom is the length times width.
Original Pool = l*w
New pool = 2l*2w = 4*l*w
FALSE

b) 4 walls is length times base times two.  Added with width times base times two.
ORiginal Pool = l*b*2 + w*b*2
New Pool = 2l*b*2 + 2w*b*2 = 2(l*b*2 + w*b*2)
TRUE

c) Area of pool is length times width times base.
Original Pool = l*w*b
New Pool = 2l*2w*b = 4*l*w*b
FALSE

The correct answer is b)