PLEASSEE HELLP!!

_Which of the following considered as isoelectronic particles? _

(a)7 N-3 ,8 O-2 , 9F-1

(b) 8 O-2 ,9 F-1, 16 s-2

(C) 18 Ar , 20 Ca+2, 11 Na+

(d) 18 Ar , 12 Mg+2, 16 s-2