One advantage of the prismoidal formula is that you can use it to
a. calculate precise volumes of all prismoids.
b. estimate the volume of solids that are combinations of other solids.
c. calculate both volume and surface area.
d. determine volumes of figures that aren't prismoids.

The prismoidal formula gives the volume of prismatoid. Prismatoid is a solid where all vertices lie on two parallel planes.It is not a universal formula for computing the volumes of solids. You can calculate precise volumes of all prismoids , and that is its advantage. so, the answer is A.