Which one of the following groupings represents a collection of isoelectronic species ? <br> (At. numbers : Cs - 55, Br - 35)

Question

( A ) $Ca^{2+}, Cs^+, Br$
( B ) $Be, Al^{3+}, Cl^-$
( C ) $Na^+, Ca^{2+}, Mg^{2+}$
( D ) $N^{3-}, F^-, Na^+$