A rectangular pool can be considered as a box(cuboid)

The SA of a cuboid is 2(LB+BH+HL)

(1) Diagonal measures 50.
Now the diagonal can be that of LB,BH or HL.

We can have 2 sides as say 35,35 where SA is > 1000
or we have a side measuring more than 49 and the other 1, where the SA<1000.

We can't say.

(B) only one side is given and obviously we can have both the cases possible.

Combined: We know one diagonal measures 50 and a side is 25. So the SA will be greater than 1000.

Hence C

Is surface are > 1000 ?

1) Diagonal = 50ft.

Say, a,b are the sides of the rectangle => a^2 + b^2 = 50^2 [spoiler]so 2(a+b) = ? Insufficient [/spoiler]

2)One side of the pool side measure 25 feet

Say a,b are the sides of the rectangle => 25^2 + b^2 = c^2 [spoiler]so 2(a+b) = ? Insufficient [/spoiler]

Using 1 and 2 [spoiler]a =25, c=50, b =25 square(3) Hence option C[/spoiler]