Evaluate Without Using a Calculator by Using Ratios in a Reference

Multiple Choice

Evaluate without using a calculator by using ratios in a reference triangle.
- $\sec 240 ^ { \circ }$

A) 2
B) $- 2$
C) $- \frac { 2 \sqrt { 3 } } { 3 }$
D) $\frac { 2 \sqrt { 3 } } { 3 }$