Which non-metal is used for making glass?

The correct answer is option 3. Silica.

Out of the options you listed, Silica is the non-metal commonly used for making glass.

Silica (Silicon Dioxide, \(SiO_2\)): This is the main component of glass, typically accounting for around 70% of its composition. Silica provides the rigid structure and strength to the glass.

Alumina (Aluminum Oxide, \(Al_2O_3\)): While alumina can be added to glass in smaller proportions, it's not the primary non-metallic component. It can improve the chemical durability and heat resistance of glass.

Graphite: This is a form of carbon and is not typically used in glass production due to its black color and opacity.

Sulphur: Sulphur is a non-metal but doesn't have the properties necessary for glassmaking. It can be used in some specialized glasses for specific applications, but it's not a common component.