Find the Measure of the Dihedral Angle Indicated $120 ^ { \circ }$

Multiple Choice

Find the measure of the dihedral angle indicated.
-The figure shown is a right prism whose bases are regular octagons. Find the measure of the dihedral angle between each lateral face and a base.

A) $120 ^ { \circ }$
B) $90 ^ { \circ }$
C) $135 ^ { \circ }$
D) $45 ^ { \circ }$