Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : Dipole-dipole interactions are the only non-covalent interactions, resulting in hydrogen bond formation.

Reason R : Fluorine is the most electronegative element and hydrogen bonds in HF are symmetrical.

In the light of the above statements, choose the most appropriate answer from the options given below :

Which among the following species has unequal bond lengths?

According to molecular orbital theory, the species among the following that does not exist is :

The correct set from the following in which both pairs are in correct order of melting point is :