I would say c
Ccccccccccccccccccccccc
Check the picture.
The bases of the 2 prisms are on 2 parallel planes,
a and
b.
Let
c be a third plane, between
a and
b, parallel to both.
Then,
the cross-sections
A and
B , of the 2 prisms, formed by plane c, have
Equal Areas,
this is by
Cavalier's Principle.