In the context of measuring the properties of galaxies, _____ are examples of a standard candle. ...

In the context of measuring the properties of galaxies, _____ are examples of a standard candle.
 
  A) Cepheid variable stars
  B) white dwarf stars
  C) M stars
  D) red giant stars

Question 2

The most luminous stars in elliptical galaxies are:
 
  A) B stars.
  B) O stars.
  C) blue supergiants.
  D) red giants.

Question 3

The _____ of active galactic nuclei (AGN) is an attempt to explain the different types of AGN using a single model viewed from different directions.
 
  A) hierarchical model
  B) hybrid hierarchical model
  C) monolithic model
  D) unified model