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

Assertion (A): $\mathrm{PH}_3$ has lower boiling point than $\mathrm{NH}_3$.

Reason (R) : In liquid state $\mathrm{NH}_3$ molecules are associated through vander Waal's forces, but $\mathrm{PH}_3$ molecules are associated through hydrogen bonding.

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

Arrange the bonds in order of increasing ionic character in the molecules. $\mathrm{LiF}$, $\mathrm{K}_2 \mathrm{O}, \mathrm{N}_2, \mathrm{SO}_2$ and $\mathrm{ClF}_3$ :

The linear combination of atomic orbitals to form molecular orbitals takes place only when the combining atomic orbitals

A. have the same energy

B. have the minimum overlap

C. have same symmetry about the molecular axis

D. have different symmetry about the molecular axis

Choose the most appropriate from the options given below: