Opacity Is

Multiple Choice

Opacity is

A) the balance between the pressure and force of gravity inside a star.
B) the force that binds protons and neutrons together to form a nucleus.
C) the force that binds an electron to the nucleus in an atom.
D) a measure of the ease with which photons can pass through a gas.
E) the temperature and density at which a gas will undergo thermonuclear fusion.