If each cube in the rectangular prism measures 1 cubic inch, what is the volume of the prism? A. 21 cubic in B. 9 cubic in C. 27 cubic in D. 18 cubic in

Each cube measures 1 cubic inch.
The volume of the prism is the sum of the volume of the cubes.
The number of cubes is 6 x 3 = 18
So the volume will be :
18 cubic inches.
ANSWER :
D. 18 cubic in