Question

What happens during one half-life of a radioactive isotope?

A. Half of the sample undergoes radioactive decay.

B. Half of the time has passed during which the sample will be radioactive.

C. Half of the sample becomes radioactive.

D. Half of the time has passed during which the sample will not change.

Answer 1

Half Life of a radioactive isotope is defined as the time in which one-half of its atom decay or disintegrate.

So, from the given options, option A is the correct answer:
During one-half life, half of the sample undergoes radioactive decay.