To find the volume of a rectangular prism, you use the formula:
\[ \text{Volume} = \text{Base Area} \times \text{Height} \]
In this case, the base area (\( B \)) is given as \( 21 , \text{cm}^2 \) and the height (\( h \)) is given as \( 3 , \text{cm} \).
Plugging in the values:
\[ \text{Volume} = 21 , \text{cm}^2 \times 3 , \text{cm} = 63 , \text{cm}^3 \]
Therefore, the volume of the right rectangular prism is \( 63 , \text{cm}^3 \).
So the correct response is: 63 cm³.