A．We have enough written record of our ancestors to prove the identity.
B．Many American slaves got to know who their ancestors were though DNA.
C．An adopted child generally lacks enough information to prove his identity.
D．Molecular genealogy can be used to prove a relationship between individuals.

A．we can decide according to their family tree
B．we can find the truth from their genetic markers
C．we can compare the differences in their Y chromosome
D．we can look for written records to prove their relationship