Be sure to explain your answeras clear as possible.

Positive exponent? An index would imply that the base, x, had a fractional exponent.

My Dear Aunt Sally used to say, "If there's a negative exponent in your face, then flip your base!"

In other words, if the exponent is negative, take the reciprocal of the base, x →  and change the exponent to positive.

Therefore:   

I have cross the fraction bar line change the exponent sign.

The answer to the question is d