Write the Number as a Product of a Real Number $i$

Multiple Choice

Write the number as a product of a real number and $i$ . Simplify the radical expression.
- $\sqrt{-4}$

A) $2 \mathrm{i}$
B) $-2 \mathrm{i}$
C) $-\mathrm{i} \sqrt{2}$
D) ± 2