Correct answer only melissa is using synthetic division to divide. which answer is correct?

Without even lifting your pencil, you can eliminate a and d. The leading coefficient has nothing to do with what you are dividing by. The question is should you be using 1 or - 1 on the outside of the division sign?  

The one you have marked is absolutely correct. You could check it by long division if you know how to do that better than synthetic division.  Set it up like this.

x - 1 || 3x^3 - x^2- 9x + 7 || 3x^2 + 2x - 7

is what you get doing it the long hard way.

C

c

Step-by-step explanation: