In the rectangular parallelepiped shown, A B=3, B C=1, and C G=2. Point M is the midpoint of \overline{F G}. What is the volume of the rectangular pyramid with base B C H E and apex M ?

**Answer Choices**

A. 1

B. \dfrac{4}{3}

C. \dfrac{3}{2}

D. \dfrac{5}{3}

E. 2