Why Are Cepheid Variables Important

Multiple Choice

Why are Cepheid variables important?

A) Cepheid variables are stars that vary in brightness because they harbor a black hole.
B) Cepheids are pulsating variable stars,and their pulsation periods are directly related to their true luminosities.Hence,we can use Cepheids as "standard candles" for distance measurements.
C) Cepheids are a type of young galaxy that helps us understand how galaxies form.
D) Cepheids are supermassive stars that are on the verge of becoming supernovae and therefore allow us to choose candidates to watch if we hope to observe a supernova in the near future.