Let f(x) be a function and let f'(a) be the derivative of f at x=a. Which of the following statements are true?

I. f'(a) is the slope of the line tangent to the graph y=f(x) at x=a
II. f'(a) is the instantaneous rate of change of f(x) at x=a

a. I and II
b. I only
c II only
d. Neither statement is true