Point are set up (x,y) you sub the number for x into the equation and see if you get the number for y.
y=4x+3
y=4 (5)+3
y=20+3
y=23
so A isn't the answer
y=4 (17)+3
y=68+3
y=71
B isn't the answer
y=4 (4)+3
y=16+3
y=19
and because 4 is the x value for c and d and there can only be 1 y value for each x you're answer is C because when x=4 y =19 or (4,19)