"which is characteristic of globular star clusters"?
only brown dwarfs in a yellow ball 100 ly across
a mix of old and young stars, about 100,000 ly across
old age and hundreds of thousands of stars, only about 30 ly wide
no remaining ms stars, but millions of white dwarfs
bright blue main sequence stars, and thousands of them

Old age and hundreds of thousands of stars, only about 30 ly wide

Explanation:

A globular cluster is a collection of stars which are bound by a very strong force known as gravity (gravity is the force of attraction between two bodies). The gravity then causes globular clusters to have a spherical shape with a high number of stars closer to the center (where the gravity is strongest).

These stars are usually very old and the diameter of the clusters are usually only 30 lightyears wide because of the strong gravity.

answer d to the question