there are 12 students total and there are two groups of students, boys and girls, 8 girls 4 boys so we take that and convert it to a fraction which would make 2/3 girls and 1/3 boys, so that would mean that boys have a 33% chance of being selected
The volume of a cylinder is base area times volume. Since we have our base area of 12 pi, and our height of 9, we have the are as 12* 9 = 108 pi inches cubed. Thus, the answer is D.