Subgroups of Symmetric Group Isomorphic to Product of Subgroups

Theorem
Let $S_n$ denote the symmetric group on $n$ letters.

Let $K \in \left[{1 \,.\,.\, n}\right]$.

Then there are $\displaystyle \binom n k$ subgroups of $S_n$ which are isomorphic to $S_k \times S_{n-k}$, where $\displaystyle \binom n k$ denotes the binomial coefficient.

All of these $\displaystyle \binom n k$ subgroups are conjugate.