Final answer:
A cathode ray oscilloscope consists of at least four main parts including the electron gun, vertical coils, horizontal coils and the screen.
Step-by-step explanation:
The cathode ray oscilloscope consists of several main parts. The cathode ray tube (CRT) is the most essential component, known for generating rays of electrons from the cathode in the electron gun. The CRT in a device like an oscilloscope utilizes magnetic fields to direct the accelerated electrons. Specifically, two pairs of coils are employed for this task: one for vertical steering and another for horizontal steering. Thus, the core answer to the student's question is that a cathode ray oscilloscope consists of at least four main parts: the electron gun, the pair of vertical coils, the pair of horizontal coils, and the screen where the electrons eventually make contact to form images or in an oscilloscope's case, to display electrical signal patterns.