to find the slope, you have to use two points so use A and B together and then C and D.
the slope formula is;
m = y2 - y1/ x2 - x1
A. (3, 4) B. (6, 1)
m = y2 - y1/ x2 - x1
m = 1 - 4/ 6 - 3
m = -3/2
C. (0, -2) D. (-3, 1)
m = y2 - y1/ x2 - x1
m = 1 - (-2)/ -3 - 0
m = 3/-3
m = -1
hope this helped, God bless!