Given;
The graph of a line.
To find:
The slope of the line.
Solution:
From the given graph it is clear that the line passes through the points (1,7) and (3,5).
So, the slope of the given line is
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
[tex]m=\dfrac{5-7}{3-1}[/tex]
[tex]m=\dfrac{-2}{2}[/tex]
[tex]m=-1[/tex]
Slope of the line is -1.
Therefore, the correct option is D.