A. Low-frequency component
B. High-frequency component
C. Low-voltage component
D. High-voltage component
The question was posed to me at a job interview.
My question is based upon Sensivity Enhancement for NMR Spectroscopy topic in section Nuclear Magnetic Resonance Spectrometer of Analytical Instrumentation
Easy explanation: In Spin Decoupler, the difference frequency circuit provides a means of mixing two signals and a filter to recover the low-frequency component. It is included to provide a read-out frequency.