Which one of the following groups represent a collection of isolectronic species ? (At.no `Cs = 55, Br = 35)`

Which one of the following groupings represents a collection of isoelectronic species ?

Which one of the following groupings represents a collection of isoelectronic species ?

Which one of the following groups represent a collection of isoelectrionic species? (At. No. Cs=55,Bt=35)

Which of the following grouping represents a collection of iso-electionic species?

Which one of the following groupinga represents a collection of isoelectronic species ? [ At.nos- Cs - 55 , Br - 35 ]

Which of the following grouping represents a collection of isoelectronic species (At. No : 'Cs=55, Br=35' )