Which equation represents the difference quotient of f(x) for all nonzero values of h?

Look at the graph thoroughly .
It passes through origin and given some points
(-1,1)
(1,-1)
(2,-2)
(-2,2)
We observe that
[tex]\\ \sf\longmapsto f(x)=-x[/tex]
Hence whatever the function be the result will be -x
Option D is correct