I think it is referring to the interior diagonal, since it says "diagonal of the cube", instead of "diagonal of a side of the cube".
1) and 2) both refer to cubes w/ a side of 10.
Diagonal simply means the highest distance between 2 points in the cube. there can be only one highest distance between 2 points. for a cube digonal is simply sqrt(square of one side + square of one side's diagonal)
if x is the length side then diagonal = sqrt(x^2+2x^2)
= sqrt(3) * x
diagonal of one side = sqrt(x^2 + x^2)
= sqrt(2) * x
so if we know that the diagonal of a cube is 10*sqrt(3)
we know that x = 10
so voluve = 1000
so statement 2 is sufficient.
surface area = 6x^2 = 600
so, x^2 = 100
so volume = 1000
there fore D is the answer.