The correct answer is a) metalloids.
Metalloids are a category of elements that possess characteristics of both metals and non-metals. They typically have a metallic luster but are brittle like non-metals. Metalloids also have intermediate electrical conductivity, meaning they can be semiconductors, which makes them useful in electronic devices. Examples of metalloids include silicon and germanium. In contrast, allotropes refer to different forms of the same element, alloys are mixtures of metals, and colloids are a mixture where tiny particles are dispersed but not dissolved in a medium.