Solve the Equation $\sqrt { 11 - p } - \sqrt { 2 + p } = - 1$

Solve the equation.
- $\sqrt { 11 - p } - \sqrt { 2 + p } = - 1$

A) $\{ 7,2 \}$
B) $\{ 2 \}$
C) $\{ \pm 2 \}$
D) $\{ 7 \}$