Metalloids are elements that possess properties that are in between those of metals and nonmetals. This means they can exhibit a mix of metallic and nonmetallic characteristics. For example, metalloids typically have a shiny or metallic luster, similar to metals, but they can also be brittle like nonmetals.
Additionally, metalloids are known for their semiconducting properties, allowing them to conduct electricity better than nonmetals but not as well as metals. This intermediate behavior is what allows them to be useful in various applications, especially in the electronics industry where semiconductors are a key component in devices like transistors and diodes.
The other options describe properties that do not accurately represent what metalloids are. Some elements that are gases at room temperature (such as oxygen and nitrogen) are not necessarily metalloids, and the definition provided in option B accurately reflects the unique characteristics of metalloids.