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Let $f(x)$ be a function such that $\lim \limits_{x \to 10} \frac{f(x)-f(10)}{x-10} =-1$. Which of the following statements must be TRUE?

$\lim \limits_{x \to 10} f(x)$ does not exist

$f(10)=-1$

$f’(10)=-1$

$f(x)$ is continuous at $x=-1$