The correct answer is A. Transistors.
Transistors are semiconductor devices used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor’s terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.
Switches are devices that allow or disallow the flow of electricity. They can be either mechanical or electronic. Mechanical switches are operated by hand, while electronic switches are controlled by electrical signals.
Diodes are semiconductor devices that allow current to flow in one direction only. They are used in a variety of applications, including rectifiers, amplifiers, and oscillators.
Buffers are devices that isolate one part of a circuit from another. They do this by providing a high impedance between the two parts. This prevents noise and interference from being passed from one part of the circuit to the other.
In conclusion, VLSI technology uses transistors to form integrated circuits. Transistors are semiconductor devices that can be used to amplify and switch electronic signals and electrical power. They are the basic building blocks of integrated circuits, and they are used in a wide variety of electronic devices.