A cylinder
There are many possible answers: a frustrum of a cone, a sphere or torus intersected by a pair of parallel planes, a circular prism (cylinder) are some.
A rectangular pyramid has no circular bases.
Half of a sphere with a circular base is called a Hemisphere.
None. By definition, a triangular prism has triangular bases. If it had circular bases it would be a circular prism (cylinder).
None because it's a circular shape.
It has 2
Only ONE!
None!
none
It has one circular base
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