One thing everyone always forgets is we don't usually see the <em>entire</em> graph. Once out of the frame, these functions can do anything they want.
From what we can see, only the bottom right one is always decreasing.
Answer: bottom right
By the way, the top right graph (a vertical line) isn't a function.
The discriminant is

which is 0.
Since the discriminant is 0, there is only one real solution.
Bom dia o sou já nasceu lá na fazendinha (8,5) é esse