(B) In asexual reproduction,the reproducing cells produce a copy of their $DNA$ through some chemical reactions. However,this copying of $DNA$ is not perfectly accurate,and therefore,the newly formed $DNA$ has some variations.
It can be observed that in asexual reproduction,very few variations are allowed. Therefore,if a trait is present in only $10\%$ of the population,it is more likely that the trait has arisen recently. Conversely,a trait present in $60\%$ of the population has had more time to spread through successive generations. Hence,it can be concluded that trait $B$,which exists in $60\%$ of the same population,has arisen earlier than trait $A$.