Question

What is the slope of the secant line between points (a,f(a)) and (b,f(b)) on the graph of f?
what is the correct formula?
A.) M sec = f(a) - f(b) over b - a
B.) M sec = f(b) + f(a) over b - a
C.) M sec = f(b) - f(a) over b - a
D.) M sec = f(b) - f(a) over b + a