Staements I: To determine the age of certain very old oragnic samples, dating of the sample with radioactive isotpes having larger half-life is a better choice than with radioactive isotopes having smaller half-lives.
Staements II: The activity of a radioactive sample having smaller half-life is negligibly small after a very long time and hence makes it next to impossible to get dtected.

Answer

a

Explanation

If the half-life of a radioactive isotope is small as compared to the age of organic sample, then over the age of the sample the activity of radioacticve isotope becomes very small and hence is impossible to detect. While this process will not arise if we use radioactive isotope having larger half-life for dating with organis samples.