Determine the Union $\boldsymbol { X } \cup \boldsymbol { Y }$

Multiple Choice

Determine the union $\boldsymbol { X } \cup \boldsymbol { Y }$ . Express the answer in interval notation.
- $X = \{ x \mid x > - 9 \}$ and $Y = \{ x \mid x \leq 16 \}$

A) { }
B) $( 16 , - 9 ]$
C) All real numbers
D) $( - \infty , 16 ] \cup ( - 9 , \infty )$