To answer this question, you need to understand the properties and applications of silicon carbide.
Option A) Making cement and glass - This option is incorrect because silicon carbide is not used in the production of cement and glass. Instead, materials such as limestone, clay, and sand are commonly used in cement and glass manufacturing processes.
Option B) Disinfecting water of ponds - This option is incorrect because silicon carbide is not used for disinfecting water. Other substances, such as chlorine or ultraviolet light, are commonly used for water disinfection purposes.
Option C) Cutting very hard substances - This option is correct because silicon carbide is widely used as an abrasive material in cutting tools. It has a high hardness and is capable of cutting through very hard substances such as metals, ceramics, and stones.
Option D) Making casts for statues - This option is incorrect because silicon carbide is not used for making casts for statues. Other materials, such as plaster or metal alloys, are commonly used for casting sculptures and statues.
Therefore, the correct answer is C) cutting very hard substances. Silicon carbide is commonly used as an abrasive material in cutting tools due to its high hardness and ability to cut through very hard substances.