All of the Following Are Drawbacks Associated with the DNA

All of the following are drawbacks associated with the DNA evidence of tracing African origins except:

A) scientists assume the DNA is originating in Africa and migrating out,but it could also be migrating into Africa.
B) mtDNA is not always passed from mother to child;sometimes,it skips a generation.
C) scientists assume that selective pressures do not affect the DNA,but there is evidence for selective pressure on mtDNA.
D) both models suggest steady rates of mutation,and mutation is notoriously uneven.
E) mtDNA studies exclude information carried on the Y chromosome.