Variables of a Certain Type Are Called Cepheid Variable Because

Multiple Choice

Variables of a certain type are called Cepheid variable because

A) the first one discovered was in the constellation of Cepheus.
B) they were discovered by Anna Marie Cepheid and her brother Raul.
C) they all lie in the Cepheus star cluster.
D) they can be used to determine the distance to Cepheid star clusters.
E) they can be used to determine the distance to all of the stars in the Cepheid galaxy.