To determine the surface area (S.A.) of a rectangular prism, the formula used is:
\[ \text{S.A.} = 2(lw + lh + wh) \]
where \( l \) is the length, \( w \) is the width, and \( h \) is the height of the prism.
Looking at the provided options, the formula that correctly represents the surface area of a rectangular prism is:
\[ \text{S.A.} = 2(2 \cdot 3) + 2(2 \cdot 4) + 2(3 \cdot 4) \]
This option expands to calculate the areas of all the rectangles that make up the surface, which is the correct method for determining the surface area.
Thus, the correct response is:
\[ \text{S.A.} = 2(2 \cdot 3) + 2(2 \cdot 4) + 2(3 \cdot 4) \]