Which one of the following sets of ions represents a collection of isoelectronic species ?

Question

( A ) $N^{3-}, O^{2-} , F^-, S^{2-}$
( B ) $K^+ , Cl^-, Ca^{2+}, Sc^{3+}$
( C ) $Ba^{2+} , Sr^{2+}, K^+, S^{2-}$
( D ) $Li^{+}, Na^{+} , Mg^{2+}, Ca^{2+}$