To calculate the volume of a cone, you can use the formula:
\[ V = \frac{1}{3} \pi r^2 h \]
where \( V \) is the volume, \( r \) is the radius of the base, and \( h \) is the height of the cone.
Given:
- The height \( h = 9 \) inches
- The diameter of the base is \( 4 \) inches, so the radius \( r = \frac{4}{2} = 2 \) inches
Now, substitute the values into the volume formula:
\[ V = \frac{1}{3} \pi (2)^2 (9) \]
Calculating the area of the base:
\[ (2)^2 = 4 \]
Now, plug that back into the formula:
\[ V = \frac{1}{3} \pi (4)(9) = \frac{1}{3} \pi (36) = 12\pi \]
Thus, the volume of the cone is:
\[ \boxed{12\pi \text{ in}^3} \]
So the correct response is \( 12\pi \text{ in}^3 \) or \( 12 \text{ pi in cubed} \).