A type II supernova (Multiple Choice)

A type II supernova
 
  a. occurs when a white dwarf's mass exceeds the Chandrasekhar limit.
  b. is the result of helium flash.
  c. is characterized by a spectrum that shows hydrogen lines.
  d. occurs when the iron core of a massive star collapses.
  e. is characterized by a spectrum that shows hydrogen lines and occurs when the iron core of a massive star collapses.

Question 2

How are astronomers able to determine that quasars are so small?
 
  a. They are variable over a short period of time.
  b. They emit mainly X-rays.
  c. They are only found at very large distance.
  d. The structure of a quasar is completely resolved in images.

Question 3

Stars with masses between 0.4-Mo and 4-Mo
 
  a. undergo thermonuclear fusion of hydrogen and helium, but never get hot enough to ignite carbon.
  b. undergo thermonuclear fusion of hydrogen, but never get hot enough to ignite helium.
  c. produce type I supernovae after they exhaust their nuclear fuels.
  d. produce type II supernovae after they exhaust their nuclear fuels.
  e. undergo carbon detonation.