ANSWER
The constant of variation is [tex]5[/tex]
EXPLANATION.
The constant of variation is the slope connect any two pairs of points.
Recall that the slope formula is given by,
[tex]m=\frac{y_2-y_1}{x_2-y_1}[/tex]
For instance using the points [tex](1,5)\:and\: (2,10)[/tex] will give the slope to be,
[tex]m=\frac{10-5}{2-1} [/tex]
[tex]m = \frac{5}{1}=5[/tex]
Therefore the constant of variation is
[tex]5.[/tex]
The correct answer is C.
