What important role does the ozone layer play in Earth's atmosphere?

What important role does the ozone layer play in Earth's atmosphere?
 
  a. The ozone layer absorbs ultraviolet photons.
 b. The ozone layer traps in infared radiation.
 c. The ozone layer produces water vapor.
 d. The ozone layer traps in UV radiation.
 e. The ozone layer produces the oxygen needed for life.

Question 2

The energy emitted from the surface of a main sequence star is less than the energy generated in the core.
 
  a. True
  b. False
  Indicate whether the statement is true or false

Question 3

Why is the very center of Earth's core a solid and not a liquid?
 
  a. There is less metal in the central core.
 b. The central core has a combination of gases with the metals.
 c. Accretion seeded Earth with a solid central core.
 d. The pressure at the central core raises the melting point of the metals higher than its temperature.
  e. The central core is a frozen block of water ice.

Question 4

There is a mass-luminosity relationship because stars support their weight by generating energy, and more massive stars have more weight to support.
 
  a. True
  b. False
  Indicate whether the statement is true or false