What distinguishes metalloids from metals and non-metals?

Metalloids are unique elements that display a combination of properties characteristic of both metals and non-metals, which is what makes option B the correct choice. This dual nature is significant in understanding the behavior and application of metalloids in various chemical and physical contexts.

For instance, metalloids can conduct electricity better than non-metals but not as efficiently as metals, which makes them useful as semiconductors in electronic devices. Additionally, their chemical properties can vary widely; they can react like metals in some situations and like non-metals in others, depending on the conditions and the specific elements involved.

The other options are incorrect because they do not accurately describe metalloids. For instance, metalloids are actually conductive to some degree, contradicting the notion that they are not conductive. They can also exist as solids at room temperature rather than being exclusively gases. Lastly, metalloids can and do form compounds, further distinguishing them from the assertion that they cannot do so.