Which of the following is not true?

Question

A. In a solid of revolution, the cross-sections are circles or washers.
B. You can figure the volume of a solid by slicing it into cross-
sections, figuring the individual volumes, and adding them up.
C. You can figure the exact volume of a solid by slicing it into cross-
sections, figuring the individual volumes by multiplying cross-
sectional area times thickness, and adding them up.
D. A solid of revolution is obtained by revolving a region about a line.
E. Figuring the volume of a solid can involve slicing it into cross-
sections.

Answer 1

Answer C (Apex)

Answer 2

It is C, I confirm.