Give an Expression That Generates All Angles Coterminal with the Given

Multiple Choice

Give an expression that generates all angles coterminal with the given angle. Let n represent any integer.
- $- 21 ^ { \circ }$

A) $- 21 ^ { \circ } + n \cdot 180 ^ { \circ }$
B) $- 21 ^ { \circ } - n \cdot 180 ^ { \circ }$
C) $- 21 ^ { \circ } + n \cdot 360 ^ { \circ }$
D) $- 21 ^ { \circ } + 2 n \cdot 360 ^ { \circ }$