Which of the following forms a dimer by $H$-bond?

The molecular interactions responsible for hydrogen bonding in $HF$ are:

Given below are two statements:
Statement $I$: $o$-Nitrophenol is steam volatile due to intramolecular hydrogen bonding.
Statement $II$: $o$-Nitrophenol has a high melting point due to hydrogen bonding.
In the light of the above statements,choose the most appropriate answer from the options given below:

In which of the following compounds is intramolecular hydrogen bonding present?

Why does $NH_{3}$ form hydrogen bond but $PH_{3}$ does not?

Intramolecular hydrogen bonding is formed in