Answer:

To determine which of the given elements is not a metalloid, we need to understand the properties and characteristics of metalloids and identify the one element that does not possess these characteristics.

Metalloids:
Metalloids, also known as semi-metals, are a group of elements that have properties intermediate between those of metals and nonmetals. They exhibit both metallic and nonmetallic properties, making them unique. Metalloids are typically solid at room temperature and have a shiny or metallic appearance. They are also generally brittle and semiconductors of electricity.

Given Elements:
a) Copper: Copper is a metal and not a metalloid. It is a good conductor of electricity and heat, possesses metallic luster, and has high ductility and malleability. Therefore, copper is not a metalloid.

b) Carbon: Carbon is a nonmetal and not a metalloid. It exists in various forms, such as graphite and diamond, which have different properties. Carbon is a poor conductor of electricity and heat, and it does not possess metallic luster. Therefore, carbon is not a metalloid.

c) Sulphur: Sulphur is a nonmetal and not a metalloid. It is a poor conductor of electricity and heat and does not possess metallic luster. Sulphur is brittle and can exist in different allotropes. Therefore, sulphur is not a metalloid.

d) Silicon: Silicon is a metalloid. It is a semiconductor of electricity and possesses some metallic properties like luster. Silicon is brittle and is used extensively in the electronics industry. Therefore, silicon is a metalloid.

Conclusion:
Among the given elements, copper is the only one that is not a metalloid. Copper is a metal, while carbon, sulphur, and silicon are nonmetals or metalloids.