The correct order of the boiling points of H2O ,  HF ,  NH3 is: 

1. HF > H2O > NH3

2. H2O > HF > NH3

3. NH> HF > H2O

4. NH> H2O > HF

HINT: Boiling point depends on the extent of hydrogen bonding.

Explanation:

Strength of H-bond is in the order H...F > H...O < H...N.
But each H2O molecule is linked to four other H2O molecules through H-bonds whereas each HF molecule is linked only to two other HF molecules. So, the extent of hydrogen boing is strong in molecules.
Hence, Boiing point order is : H2O > HF > NH3