Solve the Inequality $$x ^ { 2 } - 4 x - 21 \leq 0$$

Multiple Choice

Solve the inequality. Write the solution set in interval notation.
- $$x ^ { 2 } - 4 x - 21 \leq 0$$

A) $( - \infty , - 3 ] \cup [ 7 , \infty )$
B) $[ 7 , \infty )$
C) $( - \infty , - 3 ]$
D) $[ - 3,7 ]$