Which one of the following sets of ions represents a collection of isoelectronic species? [AIEEE 2006]

N3–, O2–, F–, S2–N3–, O2–, F–, S2–

Which one of the following sets of ions represents a collect

1.	Which one of the following sets of ions represents a collection of isoelectronic species? [AIEEE 2006]
A.	K+, Cl–, Ca2+, Sc3+
B.	Ba2+, Sr2+, K+, S2–
C.	N3–, O2–, F–, S2–N3–, O2–, F–, S2–
D.	Li+, Na+, Mg2+, Ca2+
Answer» B. Ba2+, Sr2+, K+, S2–