Correct Answer:
C. Helium
The correct answer is Helium. Helium is the second lightest element, making it an excellent choice for lifting applications such as balloons and airships. Crucially, helium is a noble gas, meaning it is chemically inert and non-flammable. This non-flammable property is paramount for safety, especially when compared to hydrogen, which is lighter but highly combustible and led to disasters like the Hindenburg.
- Argon, Neon, and Xenon are also noble gases, but they are significantly denser than helium. While they are inert, their higher density means they lack the necessary buoyancy to lift balloons or airships effectively.
- Neon is famously used in neon signs for its distinctive glow when electrified.
- Argon is often used as an inert atmosphere for welding or in incandescent light bulbs.
- Xenon has applications in specialized lighting and anesthesia.
None of these denser gases are suitable for achieving lift in aircraft.