Let \( S_{K}=\dfrac{1+2+\ldots +K}{K} \) and \(\displaystyle \sum_{j=1}^{n} S_{j}^{2}=\dfrac{n}{A}(Bn^{2}+Cn+D) \), where \( A, B, C, D\in \mathbb{N} \) and \( A \) has least value. Then:
\( A+C+D \) is not divisible by \( B \)
\( A+B=5(D-C) \)
\( A+B \) is divisible by \( D \)
\( A+B+C+D \) is divisible by \( 5 \)