Option 1: The plane of separation between the crust and mantle is known as Mohorovicic discontinuity. This statement is correct. The Mohorovicic discontinuity, also known as the Moho, is the boundary between the Earth`s crust and mantle. It was named after the Croatian seismologist Andrija Mohorovicic.

Option 2: The mantle contains more than two-third of the total material mass of the Earth. This statement is correct. The mantle is the layer between the Earth`s crust and core, and it constitutes about 84% of the Earth`s total volume. It is primarily made up of solid rock, with some small amounts of molten rock.

Option 3: The mantle is composed of the heaviest materials of the Earth. This statement is NOT correct. The mantle is primarily composed of silicate minerals, which are not the heaviest materials of the Earth. The heaviest materials, such as iron and nickel, are found in the Earth`s core.

Option 4: The inner core of the Earth is in a solid state. This statement is correct. The inner core is the innermost part of the Earth`s core, and it is believed to be solid because of the extremely high pressure and temperature conditions at