A. NO2 because the elements are both nonmetals.
Different elements emit different spectra when their electrons get excited because each element has a different arrangement of electrons surrounding the nucleus. The energy levels in which the electrons can occupy are unique to a specific element. When an electron gets excited into a higher energy level, it will eventually relax back into its original state and emit light corresponding to that energy.
Inquiring, which comes from the word inquiry which means, "an act of asking a question". In science, the first part of the scientific method is asking questions about the world around you and then after that, conducting experiments to get answers.
Metallic bond is made up from Metals as the name states it