Answer:
a cone with a radius of 4 units
Explanation:
when rotating something, this involves a circle. so, the result will always be round and never edgy. therefrom the first option is wrong.
and we are rotating a triangle. the result will have a wide base and a pointed tip. so, the third option is wrong.
the rotation does not make the basic shape smaller. so, the second option is wrong.
yes, the fourth option is correct.