Answer:
C.
Explanation:
We have been given that a cone has a radius of 3 and a height given by the expression 2a.
To find the volume of our given cone we will use volume of cone formula.
![\text{Volume of cone}=(1)/(3)*\pi r^2*h](https://img.qammunity.org/2019/formulas/mathematics/high-school/1ihni6mw17fq5p6hj6hgvlhjzyl8nk8364.png)
Upon substituting our given values in volume formula we will get,
![\text{Volume of cone}=(1)/(3)*\pi*3^2*2a](https://img.qammunity.org/2019/formulas/mathematics/high-school/qucmvf1eoslga1sl0zfuixthnn5pbcr2ku.png)
![\text{Volume of cone}=(1)/(3)*\pi*9*2a](https://img.qammunity.org/2019/formulas/mathematics/high-school/x89pk6fw6c4usk6iwsbsq14tbxjetu18ig.png)
![\text{Volume of cone}=\pi*3*2a](https://img.qammunity.org/2019/formulas/mathematics/high-school/yx1ycyt2075r2nzjtpdw3gf7yp2yf6nj0q.png)
![\text{Volume of cone}=6a\pi](https://img.qammunity.org/2019/formulas/mathematics/high-school/win4hau95p4srsxurugjpi4pvj7nj7505z.png)
Therefore, the expression
represents the volume of our given cone and option C is the correct choice.