Rewrite this imaginary number using \( i \) and then select the best choice. Make sure the answer is fully simplified. \[ \sqrt{-2} \]

The imaginary number \( \sqrt{-2} \) can be rewritten using \( i \) as follows: \[ \sqrt{-2} = \sqrt{2} \cdot i \] This is because \( i \) is defined as \( \sqrt{-1} \), allowing us to separate the negative part from the positive. So, the fully simplified form is \( \sqrt{2} i \).