The correct answer is A. Inelastic scattering of light by molecules.
C.V. Raman was an Indian physicist who won the Nobel Prize in Physics in 1930 for his discovery of the Raman effect, which is the inelastic scattering of light by molecules. The Raman effect is a phenomenon in which light is scattered by a substance, and the scattered light has a different wavelength than the incident light. This is due to the interaction of the light with the molecules of the substance, which can cause the light to be scattered in different directions and with different wavelengths. The Raman effect is a very important phenomenon in physics and chemistry, and it has many applications in these fields.
Option B, superconductivity, is the ability of a material to conduct electricity with no resistance. Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes, and it has many potential applications in technology. However, superconductivity only occurs at very low temperatures, which limits its practical applications.
Option C, controlled nuclear fission, is the process of splitting a uranium-235 atom into two smaller atoms, releasing a large amount of energy. Controlled nuclear fission is used in nuclear power plants to generate electricity.
Option D, cyclotron, is a device that accelerates charged particles using a magnetic field. Cyclotrons are used in particle physics experiments to accelerate particles to high energies.