Answer:
NH3
Step-by-step explanation:
HF is wrong
It is an ionic and not a covalent compound
H2O is wrong
The oxygen atom has 6 valence electrons. If the two oxygen atoms take one electron each, there would be 2 bond pairs and 4 electrons I.e 2 non bonding pairs available
CH4 is wrong
Carbon has 4 valence electrons, this can be taken by each hydrogen atom
NH3 is correct
Nitrogen has 5 valence electrons. The hydrogen atoms take one electron each leaving a single pair of electron on the central nitrogen atom. This gives three bond pairs and one unshared pair