Answer:
C.20 square ft
Explanation:
We are given that
Height of triangular prism=6 ft
Rectangular face of triangular prism is called lateral face of triangular prism.
Length of lateral face,l=8 ft
Breadth of lateral face,b==2.5 ft
We have to find the area of one of the lateral face of the triangular prism.
We know that
Area of rectangle=

Area of lateral face of triangular prism=
square ft
Area of lateral face of triangular prism=20 square ft
Hence,option C is true.