Which characteristic best describes carbon monoxide?

Carbon monoxide is best described as being colorless and odorless, which is a critical characteristic that contributes to its danger. Because it lacks both color and smell, it is difficult for individuals to detect its presence in the environment. This property often leads to unintentional exposure, as it can accumulate in enclosed spaces without any noticeable warning. Understanding that carbon monoxide is undetectable by human senses emphasizes the importance of proper ventilation in spaces where combustion occurs, such as homes with gas stoves, heaters, or vehicles running inside garages.

While some of the other options present characteristics that may relate to gases, they do not accurately depict the nature of carbon monoxide, leading to misconceptions about its risks and behavior in the environment.