The graph has only one root because touches the x-axis on only one point then the function has one root
we look the fuction of a parabola like
[tex](x+a)(x+b)[/tex]
where -a and -b are the roots of the function
on our case we have one root on x=1 then the value of the two number a and b must be the same
then the fuction is
[tex](x-1)(x-1)[/tex]
and right option is D
