The slope of a line defined as the unit change of its ordinate divided by the change of its abscissa. Mathematically,
m = (y2 - y1) / (x2 - x1)
Substituting the values to the equation,
m = (-2 - 3) / (5 - 1) = -5/4
Therefore, the slope of the line is -5/4. The answer is C.