. . . . . . . . is discovered by Henry Cavendish in 1766 and named it by Levassie. A. Oxygen B. Chlorine C. Helium D. Hydrogen

The correct answer is hydrogen.

• Oxygen was discovered by Joseph Priestley in 1774.
• Chlorine was discovered by Carl Wilhelm Scheele in 1774.
• Helium was discovered by Pierre Janssen and Joseph Norman Lockyer in 1868.
• Hydrogen was discovered by Henry Cavendish in 1766 and named it by Antoine Lavoisier.

Hydrogen is the lightest element in the universe and the most abundant element in the universe by mass. It is a colorless, odorless, and tasteless gas that is lighter than air. Hydrogen is a non-metallic element that is highly flammable. It is used in a variety of applications, including rocket fuel, fuel cells, and nuclear fusion.