Answer:
[tex]\text{C. } 2[/tex]
Step-by-step explanation:
Proportional functions can be represented by [tex]y=kx[/tex], where [tex]k[/tex] is a constant of proportionality and [tex](x, y)[/tex] represents any point the line passes through.
In the graph, we can see the line passes through (20, 40). Therefore, we can plug in these coordinates to find the constant of proportionality:
[tex]y=kx,\\40=k(20),\\k=\frac{40}{20}=\boxed{\text{C. }2}[/tex]
