Explanation:

- The sun is a massive ball of gas primarily composed of hydrogen and helium.

- Around 70% of the sun's mass is made up of hydrogen.

- Hydrogen undergoes nuclear fusion in the sun's core, producing energy and converting into helium.

- Option 2: Hydrogen is the correct answer.

- Helium makes up around 28% of the sun's mass, following hydrogen.

- Helium is created from hydrogen through fusion, also contributing to the sun's energy output.

- Oxygen and carbon are present in trace amounts; they are heavier elements produced in later stages of a star’s life.