Concept:Smart film changes transparency when voltage is applied. It needs a material that is both electrically conductive and optically transparent.
Explanation:Indium tin oxide (ITO) is a transparent conducting oxide. It allows electricity to flow while letting light pass through. This makes ITO essential for smart films, touchscreens, and LCDs.
Calcium carbonate is used as a filler in plastics and paints. It is not conductive.
Zinc chloride is used in batteries and as a flux, not in smart films.
Silica is used in glass and ceramics. It is an insulator, not a conductor.
Therefore, only ITO combines the required transparency and conductivity for smart films.
Answer:Option B – Indium tin oxide