Answer: The second option and the third option are true.
Explanation:
The formula of the line in slope-intercept form is:

Where m is the slope and b is the y-intercept.
By definition, the y-intercept in a direct variation is 0.
Therefore, substituting
and
into the equation, you obtain:

Then, the equation is:

As this is a line, it is a linear function.
Therefore, the second option and the third option are true.