1. determine the graph behavior at the zero(s) of the polynomial function f(x)=x^2 - 6x + 9.

a. the graph of the function touches the x-axis at x = -3 and x = 3.
b. the graph of the function crosses the x-axis at x = -3 and x = 3.
c. the graph of the function touches the x-axis at x = 3.
d. the graph of the function crosses the x-axis at x = -3.