29.
A:
The energy required to flip the spin of a proton is in the infrared region of the electromagnetic spectrum.
B:
The energy difference between the two spin states depends on the strength of the magnetic field.
C:
When energy absorption occurs, the nuclei are said to be in resonance with the electromagnetic radiation.
D:
When a proton is alignment with the magnetic field, its energy is lower than when it is aligned against the magnetic field.
The answer is: A