Which characteristic best describes propane in its natural state?

Propane, in its natural state, is characterized primarily as both colorless and odorless. This means that when propane is present in its gaseous form, it does not possess a color that could visually identify it, and it lacks any detectable odor on its own. This characteristic is crucial for safety and handling purposes because it allows for the identification of propane only through the addition of odorants, such as ethyl mercaptan, which give it a distinct smell for leak detection.

While propane is indeed flammable—an important safety aspect—the absence of color and odor in its pure state underscores the need for caution when handling it. The designation of non-toxic refers to its general safety for human exposure at low concentrations; however, this does not imply it is free from flammability concerns. The correct description emphasizes the physical characteristics of propane in its natural state before any modifications for safety.