1.) The line with the greatest slope.
The greater the slope of the line, the more upright it is. Observing the given graph, the line with the greatest slope is line a.
2.) Lines that are parallel.
Two lines are parallel if they do not have an intersection with each other at any point in the graph. We can see that line b and line d, do not intersect at any point in the graph and are thus parallel lines.
3.) Line with a negative slope
A line with a negative slope is a line that goes downwards from left to right, in the graph we can see that line e and line f goes downwards from left to right.
4.) Line that is perpendicular to the y-axis.
A line that is perpendicular to the y-axis, is a line that is parallel to the x-axis. Looking at the graph, line c is perpendicular to the y-axis.