Select the correct answer.
What is the simplest form of this expression?
x-3/x-1 + 6/x-3
A. x²+12x+15 / (x-1)(x-3)
B. x²+3 / (x-1)(x-3)
C. x+3 / (x-1)(x-3)
D. x²-6x+3 / (x-1)(x-3)
