Answer: First option.
Explanation:
The equation of a line that passes through the origin (which is the point
), has the following form:

Where "m" is the slope of the line.
By definition, Proportional relationships have this form:

Where "k" is the Constant of proportionality.
Therefore, the graph of a Proportional relationship is a straight line that passes through the origin; then:

Observe the equations provided in the exercise's options.
In this case you can identify that the only equation that has the form
explained before, is the first one:

And the Constant of proportionality is:
