Which of the following is colorless, odorless, lighter than air, highly flammable, and sometimes called swamp gas?

The correct choice is methane. Methane is a colorless and odorless gas that is lighter than air. It is highly flammable, making it a significant component in energy production and a common material in various industrial processes. The term "swamp gas" often refers to methane because it is produced during the decomposition of organic matter in anaerobic (low-oxygen) environments, such as swamps and marshes.

In addition to its production in natural environments, methane plays a critical role as a greenhouse gas in the atmosphere and is a key focus in discussions about energy sources and environmental impacts. Its flammability makes it a useful fuel source, but also highlights the importance of handling it safely to prevent fire hazards. Understanding the properties of methane is essential for those working in fields related to energy, environmental science, and safety practices in industrial settings.