Question

while researching a topic, a student has taken the following notes:

• a star cluster is a group of stars formed from the same cloud of gas and dust and held together by gravity.
• star clusters are classified based on their age, location, and gravitational binding.
• there are two types of star clusters: open clusters and globular clusters.
• open clusters are loosely bound groups of relatively few young stars.
• globular clusters are tightly bound groups of many old stars.

the student wants to highlight a difference between open clusters and globular clusters. which choice most effectively uses relevant information from the notes to accomplish this goal?
choose 1 answer:
a a star cluster is a gravitationally bound group of stars that formed from the same cloud of gas and dust.
b scientists classify star clusters as either open clusters or globular clusters based on their age, location, and gravitational binding.
c an open cluster—a loosely bound group of relatively few new stars—is one type of star cluster.
d open clusters are loosely bound groups of relatively few young stars, whereas globular clusters are tightly bound groups of many old stars.

Explanation:

• Option A only defines a star cluster in general, not highlighting the difference between open and globular clusters.
• Option B mentions classification criteria but doesn't directly contrast the two types.
• Option C only describes open clusters without comparing to globular clusters.
• Option D clearly states the difference in binding (loosely vs tightly), number of stars (few vs many), and age (young vs old) between open and globular clusters.

Answer:

D. Open clusters are loosely bound groups of relatively few young stars, whereas globular clusters are tightly bound groups of many old stars.