The correct answer is A. Induction relay.
An induction relay is an electromagnetic device that uses a magnetic field to operate a switch. When an electric current is passed through the coil of the relay, it creates a magnetic field that attracts a metal armature. This armature then closes or opens a switch, which can be used to control a circuit.
A thermocouple is a temperature sensor that uses the Seebeck effect to generate an electric voltage. The Seebeck effect is the production of an electric voltage in a circuit when two dissimilar metals are joined together and there is a temperature difference between the two junctions.
An LVDT (Linear Variable Differential Transformer) is a device that measures linear displacement. It consists of a primary coil, a secondary coil, and a magnetic core. The core is moved along the length of the primary coil, which induces a voltage in the secondary coil. The voltage in the secondary coil is proportional to the position of the core.
Option D is incorrect because it is not a complete answer. Option E is incorrect because induction relays are electromagnetic devices.