The correct answer is: C. Cutting very hard substances.
Silicon carbide is a very hard material that is often used as an abrasive. It is used in cutting tools, such as saws and drills, to cut through hard materials such as metal and stone. It is also used in abrasive papers and powders to polish and smooth surfaces.
A. Making cement and glass is incorrect because silicon carbide is not used in these processes. Cement is made from limestone, clay, and sand, and glass is made from silica sand, soda ash, and limestone.
B. Disinfecting water of ponds is incorrect because silicon carbide is not a disinfectant. Disinfectants are chemicals that kill or inactivate microorganisms, such as bacteria and viruses. Silicon carbide is not a disinfectant and does not have any antimicrobial properties.
D. Making casts for statues is incorrect because silicon carbide is not a casting material. Casting materials are used to create molds of objects, and silicon carbide is not a suitable material for this purpose.