list the correct answer with explanation from textbook radiologic science for technologists: physics, biology and protection 9th edition and what page it is from

8. Radioactivity half-life is the time:

a. It takes for half of the dose to be delivered

b. It takes for half of the mass to disappear

c. It takes for one atom to disintegrate

d. Required for radioactivity to reach one half of its original value

e. When half of the quantity now present remains

9. The difference between electrons and beta particles is:

a. Beta particles are ionizing.

b. Beta particles have higher energy.

c. Electrons have higher mass.

d. Electrons have higher velocity.

e. Their origin