Answer: An oxygen atom in heavy water has an extra neutron. A hydrogen atom in heavy water has an extra proton.
Explanation:
The answer to letter b is
they all have one thing in common and that its all made up of atoms. When these components are active it creates energy

The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore, spectroscopy can be used to identify elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances.
Answer:
B
Explanation:
Noble gases are in group 18 (neon, argon, etc)