Consider 2 point a,c and line of infinite length passing through them point b can be above line ac or below as 3 point can't be collinear, let us assume that b is below line ac now we find slop ab= Delta p and bc = delta q either of them will be greater ( assume delta p> delta q)
Similary if point b would be above line then result would be exactly opposite (delta q> p)
This is only possible when are sorted as per their x coordinate
consider 3 points
A=(x1, y1) = (1,10)
B=(x2, y2) = (2,2)
C=(x3, y3) = (4,22)
Cleary we can never see ab= -8 bc= 10 and ac= 4 so bc it's our gradient.
Thus answer is A