GENERAL KNOWLEDGE

Detailed explanation-1: -While hydrogen and helium make up most of the gases in interstellar space, tiny traces of other elements such as carbon, oxygen and iron also exist.

Detailed explanation-2: -The data indicates that hydrogen and helium make up nearly all of the nuclear matter in the universe. The most abundant element, hydrogen, accounts for 74% of the mass while helium contributes 25%.

Detailed explanation-3: -The key difference between hydrogen and helium is that hydrogen is a diatomic gas, while helium is a monatomic gas. Hydrogen and helium are the first two elements in the periodic table. Both are gases and have a high abundance in the universe.