There are certain ______ when you have to interrupt people who are in the middle of doing something.

A．DNA is characteristic of a region
B．they are beyond doubt of common ancestry
C．DNA strand has the ability to identify individuals
D．their unique identification can be provided via DNA

A．genetics has achieved a breakthrough
B．genetic information contained in DNA can be revealed now
C．each individual carries a unique record of who he is and how he is related to others
D．we can use DNA to prove how distant an individual is to a family, a group or a population