To find the surface area of the triangular prism, we need to find the area of each of the three parallelogram faces and the area of the two triangular faces.
The area of each parallelogram face is base times height, which is 12 cm times 4 cm, giving us 48 cm^2 for each face. Since there are three parallelogram faces, the total area for them is 144 cm^2.
The area of each triangular face is base times height divided by 2, which is (9 cm times 12 cm) divided by 2, giving us 54 cm^2 for each face. Since there are two triangular faces, the total area for them is 108 cm^2.
Adding up the areas of all five faces, we get a total surface area of 144 cm^2 + 108 cm^2, which is equal to 252 cm^2.
Therefore, the answer is B) 252 cm^2.