What is the primary characteristic of an elliptical galaxy?

An elliptical galaxy is primarily characterized by its composition and structure, which include mainly older stars and very little gas. Unlike spiral galaxies that feature distinct arms and ongoing star formation, elliptical galaxies tend to have a smoother, more rounded shape and are largely populated by older stellar populations. This lack of gas indicates that there is minimal ongoing star formation, as gas is a critical component needed for the birth of new stars.

The absence of bright regions typically associated with active star formation, as seen in spiral galaxies, further emphasizes the older, more evolved state of the stellar population in elliptical galaxies. This characteristic helps distinguish them from other types of galaxies, making option B the accurate description of an elliptical galaxy's primary feature.