What is a characteristic of propane?

Propane is primarily characterized by its properties as a gas at room temperature and its odorless nature in its unprocessed form. In its natural state, propane does not have a distinctive smell, which is significant for safety reasons; an odorant is often added to help detect leaks. This characteristic is vital because, while propane itself lacks odor, the added odorant enables individuals to recognize possible gas leaks, promoting safety in its use.

The other options do not correctly describe propane. It does not exist as a solid at room temperature; instead, it is a gas. Propane also has a relatively low boiling point, which is contrary to the notion of having a high boiling point, and while high concentrations can be harmful, propane itself is not classified as toxic under normal usage conditions when safety guidelines are followed. Therefore, the characteristic of being odorless aligns correctly with the properties of propane.