Which of the molecules can be involved in hydrogen bonding?
hf
ch3oh
ch4
h2

HF & CH3OH

Explanation:

Hydrogen bonds are formed as a consequence of  the attractions between a partially positive hydrogen (δ+ hydrogen) atom of a molecule and a lone pair of another electronegative element, such as a nitrogen, oxygen or fluorine molecule of another molecule.

In the case of HF, the partially positive hydrogen atom makes a hydrogen bond with the lone pair of a fluorine atom of another HF molecule in its proximity.  

In the case of CH3OH, the partially positive hydrogen atom (bound to Oxygen) makes a hydrogen bond with the lone pair of an oxygen atom of  another CH3OH molecule in its proximity.  

a:

by the combination of an unlimited number of elements