Correct Option: D

A spectrometer is an istrument used to measure properties of light over a specific portion of the electromagnetic spectrum. Cathode ray oscilloscope is an electronic display device containing cathode-ray tube (CRT) that generates an electron beam that is used to produce visible patterns or graphs on a phosphorescent screen. A sonometer is an apparatus made of hollow box having two holes. A string is attached to it by which the transverse vibrations of strings can be studied.