A) Steam engine: A steam engine operates by converting thermal energy (from steam) into mechanical work. This process is fundamentally governed by the Laws of thermodynamics, which describe how heat and work are related. Thus, A matches with II. B) Electron microscope: An electron microscope uses a beam of electrons instead of light to image a sample. The resolving power of an electron microscope is much higher than a light microscope because electrons, when accelerated, have a much shorter de Broglie wavelength than visible light. This relies on the wave nature of electrons, a concept from quantum mechanics (de Broglie hypothesis). Thus, B matches with III. C) Non-reflecting coatings: These coatings are thin films applied to optical surfaces to reduce reflection. They work by manipulating the phase of light waves. Light reflected from the top surface of the coating and light reflected from the bottom surface of the coating (at the coating-glass interface) interfere destructively, thereby reducing the overall reflected light. This phenomenon is Interference of light. Thus, C matches with IV. D) Tokamak: A Tokamak is a device that uses a strong magnetic field to confine plasma within a toroidal chamber for nuclear fusion research. The charged particles in the plasma are held in place by the magnetic field, preventing them from interacting with the reactor walls and maintaining the extremely high temperatures required for fusion. This principle is Magnetic confinement of plasma. Thus, D matches with I.