we have that
A rectangle with points (0,0), (3,0), (3, 7), and (0,7)
using a graph tool
see the attached figure
if the rectangle is rotated around the y-axis
then
the three-dimensional figure formed is a cylinder with radius 3 units and height 7 units
and
the vertical cross-section is a rectangle with 6 units x 7 units
the answer is
rectangle