21.Where do you think is the passage from?
A. Newspaper. B. Gazette. C. Journal. D. Science magazine.

22.Which of the following is not the features of mammals that distinguish them from the reptiles?
A.They¡¯re warmª²blooded.
B.They have a set of teeth of different shapes.
C.The first period of development of young mammals is within their mother¡¯s body.
D.There¡¯s some association between mother and infant.

23.Which can be inferred from the passage?
A.Mammals developed from the reptiles.
B.The animals that are hatched from eggs have no opportunity for learning.
C.Mammals developed at the cost of the extinction of reptiles.
D.Not all the primates are mammals.

24.Primates are social animals because.
A.they are handª²feeders B.of their anatomical features
C.they are arboreal D.they depend on each other

25.What leads to the features of the primate anatomy?
A.Their treeª²climbing and treeª²dwelling life.
B.Their diet.
C.The way they behave.
D.The social emphasis in their life.