Ahalf-life of a radioactive substance is the amount of time needed for one half of to decay into a stable isotope.

the neutrons in the nuclei

its beta particles

the nuclei in a sample

The correct answer is the nuclei in a sample.

Explanation:

Half life is defined as the time taken for half of the reaction to complete. This is also defined as the time in which the concentration of a reactant is reduced to half of its original value.

General expression for half life period of a reaction for nth order is:

where, n = order of the reaction

Hence, the correct answer is the nuclei in a sample.

i think it is dna, i'm not totally sure but i think it might be.

the answer would be knowledge about cars!