A6. The function $f(x)=\frac{x^{2}+5 x+4}{x^{2}+6 x+9}$ changes sign:
(A) never
(B) once
(C) twice
(D) three times
(E) four times

## II. PART
A6. Since $f(x)=\frac{x^{2}+5 x+4}{x^{2}+6 x+9}=\frac{(x+4)(x+1)}{(x+3)^{2}}$, the graph of this rational function has two zeros of the first degree and one pole of the second degree, hence it changes sign twice.

II. PART