Answer:
The same
Explanation:
Half life is the time taken for the number of atoms in a radioactive sample to decrease to half of the initial number of atoms. It is also the time taken for the activity of a radioactive sample to decrease to half of its original value.
If samples A and B were obtained from the same rock, then they contain the same number of atoms having the same initial activity even though the samples were not prepared in the same way for analysis.
Hence, samples A and B have the same half life.
