The hydrides of the first elements in groups 15-17, namely `NH_(3), H_(2)O` and HF respectively show abnormally high values for melting and boiling points. This is due to
A. small size of N,O,F
B. the ability to form extensive intermolecular H-bonding
C. the ability to form extensive intramolecular
D. effective van der Waals interaction
