Concept:Metalloids are elements that show properties intermediate between metals and non-metals.
Explanation:Metalloids are located along the zigzag line in the periodic table that separates metals from non-metals.
Typical examples include boron, silicon, germanium, and arsenic.
Among the given options, carbon and oxygen are non-metals.
Sodium is a metal because it easily loses electrons.
Silicon has both metallic and non-metallic characteristics.
It has a shiny appearance but acts as a semiconductor, which is a key property of metalloids.
Therefore, silicon is the correct choice.
Answer:C. Silicon