It is possible to date the rocks by comparing the amount of specific radioactive isotopes they contain. Which of the statement is correct in this respect:

A: Older sediment layers have equal amount of these reaioactive isotopes as that of the young ones

B: Older sediment layers have less amount of these reaioactive isotopes as that of the young ones.

C: Older sediment layers have greater amount of these radioactive isotopes as that of the young ones.

D: Older sediment layers did not have these radioactive isotopes