Solve the Quadratic Equation Using the Most Efficient Technique (Factoring $x^{2}+5 x-84=0$

Multiple Choice

Solve the quadratic equation using the most efficient technique (factoring, extracting square roots, completing the square, or the quadratic formula) .
- $x^{2}+5 x-84=0$

A) $\{12,7\}$ .
B) $\{-12,1\}$
C) $\{12,-7\}$
D) $\{-12,7\}$