Explanation

(b) A diode is a component that restricts the direction of movement of charge carriers. It allows an electric current to flow in one direction but essentially blocks it in the opposite direction. Thus, acting as a rectifier.
Thermocouples are a widely used type of temperature sensor and can also be use as a means to convert thermal energy into electrical energy.
Triode is a type of vacuum tube consisting of filament or cathode grid and plate or anode. It is used as an amplification device. Transistor is a solid state semiconductor device that can be used for amplification, switching, voltage stabilization, signal amplification etc.