Which statement best describes the major components commonly found in galaxies?

• A. Stars, Gas, and Dust
• B. Planets and Comets
• C. Oceans and Atmosphere
• D. Rocks and Ice

Answer: (A)

Galaxies are made up mainly of stars, gas, and dust. Stars provide most of the light we see and are the long‑term energy sources of the galaxy. Gas fills the spaces between stars and serves as the raw material for new stars, existing in different phases from hot ionized gas to cold molecular clouds. Dust grains mixed with the gas absorb and scatter light, help cool gas to allow star formation, and contribute to infrared emission that reveals hidden regions of a galaxy. Planets and comets, oceans and atmosphere, and rocks and ice are features associated with individual planets or moons, not the bulk components that define a galaxy.