The correct answer is: Uranium.
Uranium is a radioactive metal that is used in nuclear power plants and nuclear weapons. It is the most important mineral deposit in Manipur in terms of commercial value.
Limestone is a sedimentary rock that is composed of calcium carbonate. It is used in the construction industry and in the manufacture of cement.
Chromite is an iron ore that is used in the manufacture of steel.
Clay is a sedimentary rock that is composed of clay minerals. It is used in the manufacture of ceramics and in the construction industry.
Uranium is the most important mineral deposit in Manipur in terms of commercial value because it is a valuable resource that is used in a variety of industries. Limestone, chromite, and clay are also important mineral deposits in Manipur, but they are not as valuable as uranium.