Explanation:
the slope of a line is expressed as the ratio y/x indicating how many units y changes, when x changes a certain amount of units.
AB changes from B to A : x 1 unit (from 3 to 4), y 1 unit (from 1 to 2).
slope = 1/1 = 1
CD changes from C to D : x 7 units (from -6 to 1), y 1 unit (from 0 to 1).
slope = 1/7
the 2 lines are neither parallel nor perpendicular.
parallel lines have the same slope, which is not the case here.
the slopes of perpendicular lines are the inverse ratios with alternating sign. like 3 and -1/3.
but this does not apply to 1 and 1/7.