Which is the graph of y = _0.4x?

a.

b.

c.

d.

Y = -0.4x

1) It is a straight line
2) I passes through the origin (0,0), because the y-intercpet is 0.
3) The slope is negative, so it passes throuh II and III quadrants
4) The magnitude of the slope = 0.4
4) The angle of the line with the negative side of the x-axis is that whose tan is 0.4 => angle = 21.8 °

With all that information you can identify the graph, given that you didn't include the options.