The correct response is:
the volume of the pyramid is Start Fraction 1 over 3 End Fraction the size of the volume of the prism.
This is because the volume of a pyramid is given by the formula:
\[ V_{\text{pyramid}} = \frac{1}{3} \times \text{Base Area} \times \text{Height} \]
While the volume of a prism is calculated as:
\[ V_{\text{prism}} = \text{Base Area} \times \text{Height} \]
Since both the prism and the pyramid have congruent triangular bases and the same height, the volume of the pyramid is one-third the volume of the prism.