Answer:

Step-by-step explanation:
From the way the answers are presented, it can be seen that x refers to the radius of the base of the cone
radius: 
and we are told that the height is twice the radius, so:
height: 
and now we use the formula to calculate the volume of a cone:

where
is volume,
is radius, and
is the height. and
is a constant
in this case


so we substitute thisvalues in the formula for the volume:

Rearranging the terms

which is option A.