Without Using a Calculator, Give the Exact Trigonometric Function Value $\frac { 1 } { 2 }$

Multiple Choice

Without using a calculator, give the exact trigonometric function value with rational denominator.
-sec 30°

A) 1
B) $\frac { 1 } { 2 }$
C) $\frac { 2 \sqrt { 3 } } { 3 }$
D) $\sqrt { 2 }$