If its a triangular prism then you use the equation V = ½ × length × width × height, or V = the area of the base × the height. After that you find the area of the base by multiplying ½ × the length and width of one of the triangular bases of the prism. Then, locate the height, and multiply the height by the area of the base... But I don't know if this is what you were asking, so just in case
A is the answer since if you graph it, it has those points, or you may just simply plug in the x points that are given and see if they equal the y number