In the following questions two or more options may be correct.
CO is isoelectronic with
Isoelectronic species are the atoms of different elements with the same number of electrons.
Both (i), (ii) have 14 electrons and CO also has 14 electrons (6 electrons of C and 8 electrons of Oxygen).
SnCl2 has 84 electrons (50 electrons of Sn and 34 electrons of Cl2 ) and NO2 has 23 electrons (7 electrons of N and 16 electrons of O2).