Answer:
In short, you are looking a diagonal line passing through the origin. And yes diagonal line is a straight-edged line that is running diagonally.
Explanation:
If you want a better answer you can post the graphs.
I will tell you the trick, direct variations is another words for the relation is proportional.
The graph will have equation y=kx where k (k can't be zero) is the slope and your y-intercept is 0. The graph should be a diagonal line.
In short, you are looking a diagonal line passing through the origin. And yes diagonal line is a straight-edged line that is running diagonally.