29.Teaching machines are devices that can store instructionally information,

A

present displays,receive responses from a learner,and act on those responses.

B C.D

30.Challotte Perkins Gilman Is known primarily as an author of short stories,

A B

but she also wrote an influential book argued for equal economic opportunities for

C D women.

31.In some areas of the United States,unfavorable climate or soil make farming

A B C

an impossible task.

D

32.Naturalists have identified at least four hundred of species of mammals and

A B

six hundred types of birds in the state of California.

C D

33.Instead of tooth,the blue whale has a row of bony plates in its mouth

A B C

that functions as a food-collecting device.

D

34.Murres are black-and-white driving birds that mate every five or six years and

A

lay only a single egg at time.

B C D

35.A bar code consists a pattern of lines and bars that a computer can translate

A B C

into information.

D

36.Hummingbirds are the only birds that can fly to backwards.

A B C D

37.Fluorine,a greenish-yellow gas that is slightly heavy than air is poisonous

A B C

and corrosive and has a penetrating and disagreeable odor.

D

38.The Everglades,a large swamp area is an unique wilderness extending over

A B C

much of southern Florida.

D

39.Each year millions of tons of fertile topsoil that could produce good crops

A B C

washed away by rains.

D

40.Since the 1950's,folk'music has had a significant influence on many popular

A B C D

vocal and instrumental music.