___________ in other galaxies should contain luminous O and B ...

[tth]

___________ in other galaxies should contain luminous O and B stars if they are like the Milky Way.
 
  a. The halos
  b. The bulges
  c. The spiral arms
  d. The globular clusters
  e. The coronas

Question 2

For what kinds of stars are the masses of stars in the H-R diagram orderly? For what kinds of stars are they disorderly? In other words, could you guess the mass of a star from its location (luminosity, temperature) on the H-R diagram?
 
  What will be an ideal response?

[honnalora]

Answer to Question 1

c

Answer to Question 2

The masses of main-sequence stars decrease systematically from upper left to lower right in the H-R diagram, but the masses of giants and supergiants are not arranged in any ordered pattern.