During the annihilation of matter and antimatter, what percentage of the mass of the colliding ...

During the annihilation of matter and antimatter, what percentage of the mass of the colliding particles is converted into energy?
 
  A) 0.7
  B) 0.07
  C) 70
  D) 100

Question 2

A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth,
 
  Andrea rides on a space ship which travels away from Earth at a speed of 0.6c for five years (as measured by Courtney), then turns around and comes back at 0.6c. When Andrea returns, Courtney is 20 years old. How old is Andrea upon her return?
  A) 10 years
  B) 12 years
  C) 15 years
  D) 18 years
  E) 20 years

Question 3

At what angle, with the surface, must light strike glass (refractive index 1.6 ) in order to completely polarize the reflected ray?
 
  A) 32
  B) 86.
  C) 34.
  D) 11.
  E) 56.