Which of the following compounds will have the maximum hydrogen bonding?

Which of the following molecules shows intramolecular hydrogen bonding?

What is the maximum number of hydrogen bonds in which a single water molecule can participate?

The maximum number of hydrogen bonds that a molecule of water can have is

The boiling point of water is higher than that of liquid $HF$. The reason is that

The variation of the boiling points of the hydrogen halides is in the order $HF > HI > HBr > HCl$. What explains the higher boiling point of hydrogen fluoride?