Answer:
Valence electrons.
Explanation:
Electron, proton and neutron are the sub atomic particles of the atoms. The electrons revolve around the nucleus whereas the protons and neutron remains inside the nucleus.
The water contains hydrogen and oxygen. The electrons are shared between the hydrogen and oxygen to form the new compound water. The electrons participate in the formation of compound because they are present outside the nucleus.
Thus, the correct answer is option (D).
