The correct answer is: B. Yoke
A yoke is an electromagnetic coil that is used to deflect the electron beam in a cathode ray tube (CRT). The yoke is typically made of a soft iron core that is surrounded by a coil of wire. When current is passed through the coil, it creates a magnetic field that attracts or repels the iron core. This movement of the core causes the electron beam to be deflected in the desired direction.
A transformer is a device that transfers electrical energy from one circuit to another by means of electromagnetic induction. A capacitor is an electrical device that stores energy in an electric field. A diode is a semiconductor device that allows current to flow in one direction only.
In a CRT, the yoke is used to deflect the electron beam so that it can hit the phosphors on the inside of the screen. The phosphors then emit light, which creates the image on the screen. The yoke is also used to focus the electron beam so that it hits the phosphors in a small spot. This ensures that the image on the screen is sharp and clear.
The yoke is an important part of the CRT and it plays a vital role in creating the image on the screen.