The gas commonly used in balloons is:

🧠 Explanation:

Helium, commonly used in balloons, is a light, inert gas that provides lift due to its low density. Second only to hydrogen in lightness, it’s safer, being non-flammable. Helium fills balloons for celebrations, scientific experiments, and weather monitoring, enabling them to float high. Its scarcity on Earth, extracted from natural gas, makes it valuable. Helium’s use extends to medical and industrial applications, but its role in balloons is iconic. Understanding its properties highlights its importance in science and recreation, reflecting the balance of resource use and availability in modern applications.