Concept:Silicon is a common element found in the Earth's crust, mostly in the form of silica (SiOâ‚‚) which is the main component of sand.
Explanation:Sand is primarily made of silicon dioxide (silica).
Silicon makes up about 27.7% of the Earth's crust by mass.
Limestone contains calcium carbonate, not silicon.
Salt is sodium chloride, with no silicon.
Clay contains aluminium silicates, but pure silicon is obtained from sand.
Therefore, silicon is present in sand.
Answer:A. Sand