Simplify the Exponential Expression $49 ^ { 1 / 2 }$

Multiple Choice

Simplify the exponential expression. Write any negative exponents as positive exponents. Assume all variables represent positive real numbers.
- $49 ^ { 1 / 2 }$

A) $\frac { 1 } { 7 }$
B) 7
C) $- \frac { 1 } { 7 }$
D) $- 7$