Write the Set Using Interval Notation $\{x \mid x \leq-9\}$ A) $[-9, \infty)$

Write the set using interval notation.
- $\{x \mid x \leq-9\}$

A) $[-9, \infty)$
B) $(\infty,-9]$
C) $(-\infty,-9]$
D) $[-9,-\infty)$