What is the force that keeps a main sequence star from collapsing on itself?

What is the force that keeps a main sequence star from collapsing on itself?
 
  A) Magnetism
  B) Gravitation
  C) The strong force
  D) Radiation pressure
  E) Electron degeneration pressure

Question 2

What is the minimum temperature for a cloud to excite emission lines from H2?
 
  A) 10 K
  B) 30 K
  C) 100 K
  D) 300 K
  E) 1000 K

Question 3

Sunspots are only about 2,000 K cooler than the much brighter photosphere.
 
  Indicate whether the statement is true or false

Question 4

Which of these seems the best present answer to the horizon and flatness problems?
 
  A) The superforce rules creation.
  B) Dark Energy speeds the universe on out to infinity.
  C) symmetry in creation of particles and antiparticles
  D) the inflationary epoch
  E) the GUT theory

Question 5

Mars has a weak magnetic field.
 
  Indicate whether the statement is true or false

Question 6

Which statement about the stages of starbirth is FALSE?
 
  A) At stage 1, only the cloud exists.
  B) By stage 3, the star has formed a photosphere.
  C) Nuclear reactions begin in the core by stage 4.
  D) The T-Tauri wind is prevalent in stage 5.
  E) By stage 7, the star has reached the main sequence.