Which one of the following statements regarding 'glass' is not correct ? (a) Glass is called a 'super-cooled' liquid. (b) Main ingredients for the manufacturing of glass are silica, soda ash, borax, alumina and waste glass. (c) Particular metal oxides are added to prepare coloured glasses. (d) Minor amount of arsenic trioxide is added to lower the melting point.

Statement (d) is incorrect. Arsenic trioxide ($As_2O_3$) is primarily added to glass as a fining agent (to remove air bubbles) or as a decolorizing agent to neutralize the green tint caused by iron impurities. It is not used to lower the melting point; that role is performed by fluxes like soda ash (sodium carbonate) or potash.

• Statement (a): Glass is considered a super-cooled liquid because it is an amorphous solid that lacks a long-range crystalline structure.
• Statement (b): The manufacturing process involves silica (sand), soda ash (flux), limestone (stabilizer), alumina, and cullet (recycled waste glass).
• Statement (c): Coloured glass is produced by adding specific metal oxides; for example, cobalt oxide produces blue glass and chromium oxide produces green glass.