Star Clusters Are Important to Our Study of the Lives

Star clusters are important to our study of the lives of high-mass versus low-mass stars because

A) stars in each cluster all formed at about the same time all with the same mass.
B) the sun was once a member of a globular cluster.
C) stars in each cluster all formed at about the same time but with differing masses.
D) stars in each cluster all formed at different times with differing masses.
E) all of the above.