You Observed Three Different Star Clusters and Found That the Main-Sequence

Multiple Choice

You observed three different star clusters and found that the main-sequence turnoff stars in Cluster 1 had spectral type F, the main-sequence turnoff stars in Cluster 2 had spectral type A, and the main-sequence turnoff stars in Cluster 3 had spectral type G. Which star cluster is the youngest and which one is the oldest?

A) Cluster 1 is the youngest and cluster 2 is the oldest.
B) Cluster 2 is the youngest and cluster 1 is the oldest.
C) Cluster 2 is the youngest and cluster 3 is the oldest.
D) Cluster 3 is the youngest and cluster 1 is the oldest.
E) Cluster 3 is the youngest and cluster 2 is the oldest.