Which table shows a linear function? you!

Between all points the slope(=(y2-y1)/(x2-x1)) has to be the same:
first graph: [-5,-3] has a slope of 0.5, [-1,1] has a slope of 2 -> not a linear function
second graph: [-4,-3] has a slope of -3, [-3,-2] has a slope of -1 -> not a linear function
third graph: slope matches for all subsection->is a linear function
fourth graph: [-4,-3] has a slope of +1, [-3,-2] has a slope of +2 -> not a linear function

-> the third graph is the only given linear function

Iam guessing c. or d.