Write in Terms of I $\sqrt { - 9 }$ A) $- 3 \mathrm { i }$

Write in terms of i.
- $\sqrt { - 9 }$

A) $- 3 \mathrm { i }$
B) $- \mathrm { i } \sqrt { 3 }$
C) $3 \mathrm { i }$
D) $\pm 3$