Atomic number of (B)=Z and is a noble gas. Atomic No. of (A)=Z−1 (i.e., is a Halogen) Atomic No. of (C),=Z+1 (i.e., is a alkaliu metal) At No. of (D)=Z+2( i.e., alkaline earth metal) Hence, element (A) must be a Halogen, so has highestelectron affinity among the given species. ( C) is an alkali metal and (D) is an alkaline earth metal.