What is the graph of the rational function?

y = [ x^2 - 4x  + 3 ]  / [ x^2 - 9 ]     factor numerator, denominator  

y =  [ ( x - 1) (x - 3) ] / [ (x + 3) ( x - 3) ]    simplify

y  =  ( x - 1) / ( x + 3)

Since we have same power / same power, this graph will have a horizontal asymptote at y= 1  and a vertical asymptote at  x  = -3

"D"  is the correct answer

Here is the graph :  https://www.desmos.com/calculator/ngyzzm8hdr