Answer:
B) Cone
Explanation:
Given a right triangle being rotated about the line.
without loss of generality, assume the left corner vertex is the origin and the horizontal line is x axis
WE have the line equation of the form y =mx which is rotated about x axis.
The top vertex forms a circle when rotated about x axis. The origin becomes invariant, in other words, origin remains a point even after rotation.
So we get a figure with top a point and base a circle symmetrical about middle line
This is nothing but a cone.