Acontainer holds a pure sample of a radioactive substance with a half-life of 2 hours. which of the following statements are true?

a) after 1 hour, less than 50 % of the original atoms in the container will have decayed.
b) after 1 hour, more than 50 % of the original atoms in the container will have decayed.
c) after 2 hours, 50 % of the original atoms in the container will have decayed.
d) after 4 hours, 25 % of the original atoms will have decayed.
e) after 4 hours, the total number of atoms in the container will be reduced by 75 %.