Simplify the number using the imaginary unit i:

(square root) - 28

options:

a. 2 (square root) - 7

b. - 2 (square root) - 7

c. i (square root) 28

d. 2i (square root) 28

We have to simplify:

√ ( - 28)

We know that √ (-1) = i (the imaginary unit)

√ ( - 28) = √ 28 * ( - 1) = i √ (28) = i √ (4 * 7) = 2 i √ (7)

But there is not such solution among the options.

Only correct answer (using the imaginary unit) is:

C. i (square root) 28