The answer is B) 1/3.
There are 6 faces on a rectangular prism, each of which is a rectangle.
The area of the front and back is given by 25(8) = 200 sq. cm.
The area of the bottom and top is given by 25(4) = 100 sq. cm.
The area of the right and left is given by 4(8) = 32.
There are 2 faces out of 6 with an area that is not a multiple of 100; 2/6 = 1/3.