What is the force that keeps a main sequence star from blowing apart?

What is the force that keeps a main sequence star from blowing apart?
 
  A) magnetism
  B) gravitation
  C) the strong force
  D) radiation pressure
  E) electron degeneration pressure

Question 2

Define absorption and emission lines.
 
  What will be an ideal response?

Question 3

The most abundant molecule in molecular clouds is
 
  A) H2.
  B) He2.
  C) CO.
  D) H2O.
  E) HHe.

Question 4

Detailed study of stellar spectra in 1897, which enabled the development of the H-R diagram, was performed by:
 
  A) E.C. Pickering.
  B) Harlow Shapley.
  C) James Lick.
  D) John Herschel.
  E) Antonia Maury.

Question 5

While Mars is half as big as the Earth in diameter, its surface gravity is only about 40 as strong as the 1 g we experience here on Earth.
 
  Indicate whether the statement is true or false