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