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Now listen to the following recording and answer questions 20 to 22
20
A.Character.
B.Smell.
C.Gene.
D.Age.
21
A.The friends' genes are more different than that of the strangers.
B.The friends are as biologically close as their brothers.
C.The friends must have shared a common ancestor.
D.The friends have more DNA in common than strangers do.
22
A.It offers us more pleasure.
B.It helps us to survive.
C.It helps us to make friends.
D.It makes us better understood.
