The steepest slope is basically the slope with the greatest absolute value. You can find slope by finding rise over run when given the graphs and finding change in y/change in x in the tables.
Function 1: -3
Function 2: (13-10)/(6-3) = 3/3 = 1
Function 3: 2
Function 4: (-4-(-12))/(2-4) = 8/-2 = -4
Function 4's slope has the greatest absolute value.
answer: the fourth one