The Main Difference Between Cepheid Stars and RR Lyrae Stars

Multiple Choice

The main difference between Cepheid stars and RR Lyrae stars is:

A) their masses
B) that Cepheids form at much greater distances from Earth
C) that RR Lyrae were discovered much earlier than Cepheids
D) their pulsation mechanisms
E) that Cepheids obey a period-luminosity relation, but RR Lyraes do not