Which of the Following Statements Is TRUE

Which of the following statements is TRUE?

A) A common reference compound for ¹H and ¹³C NMR is tetramethylsilane.
B) Nuclear magnetic resonance spectroscopy uses the fact that some atomic nuclei, such as ¹H and ¹³C, have two nuclear spin states with different energies when exposed to a high potential difference.
C) The energy difference between two nuclear spin states corresponds to the energy of photons in the microwave part of the electromagnetic spectrum.
D) The energy difference between two nuclear spin states depends on the number of protons and neutrons in the atomic nucleus.
E) The difference in absorption frequency of a nucleus outside the magnetic field and a nucleus inside the external magnetic field is called the chemical shift.