What type of celestial body is primarily made up of hydrogen and helium?

The correct answer is a star, as stars are primarily composed of hydrogen and helium. These elements are the most abundant in the universe and play a crucial role in the process of nuclear fusion that occurs in a star's core. During fusion, hydrogen atoms combine to form helium, releasing vast amounts of energy in the form of light and heat, which is what makes stars visible and provides energy to surrounding planetary systems.

In contrast, planets, dwarf planets, and asteroids have different compositions. Planets often have a mix of elements and compounds, including heavier elements and compounds such as silicate rocks and metals, along with gases, depending on their classification (like terrestrial or gas giants). Dwarf planets share similar characteristics with regular planets but are not cleared of other debris in their orbits, and asteroids are primarily made up of metal and rocky materials. Therefore, the composition of stars being dominated by hydrogen and helium distinctly defines them in contrast to the other celestial bodies listed.