Choose the best reason that the function $\displaystyle f(x)=\frac{x^2-49}{x+7}$ is discontinuous at $a=-7$.

A. $\lim_{x\to a} f(x) \not = f(a)$

B. $\lim_{x\to a} f(x)$ doesn't exist.

C. The function is not defined at $a$.

Answer: