For finding the distance to M31, Hubble relied upon A) ...

[theo]

For finding the distance to M31, Hubble relied upon
 
  A) planetary nebulae near its core.
  B) Cepheid variables in its spiral arms.
  C) Type I supernova in its core.
  D) Type II supernova in its spiral arms.
  E) RR Lyrae stars in its globular clusters.

Question 2

The brightest stars in aging globular clusters will be
 
  A) blue supergiants like Rigel and Deneb.
  B) massive blue main-sequence stars like Spica.
  C) blue stragglers.
  D) red supergiants like Betelgeuse and Antares.
  E) core stars of planetary nebulae.

[ciecieme]

Answer to Question 1

B

Answer to Question 2

D

[theo]

TYSM

[xiazhe]

Excellent