Answer
See below.
Work Step by Step
By definition, we have:
$\binom p {r}=\frac{p!}{(p-r)!(r)!}$
As $p$ is a prime number and $0\lt r\lt p$ and $0\lt (p-r)\lt p$, we know that the number $p$ in the numerator can not be cancelled out (the denominator does not contain a factor of $p$).
Thus the value is divisible by $p$.
