21.Underlying aerodynamics and all other branches of theoretical mechanics are the

A B C

laws of motion who were developed in the seventeenth century.

D

22.Was opened in 1918,the Phillips Collection in Washington,D.C.,was the first

A B

museum in the United States devoted to modern art.

C D

23.A mortgage enables a person to buy property without paying for it outright;thus

A B C

more people are able to enjoy to own a house.

D

24.Alike ethnographers,ethnohistorians make systematic observations,but they also

A B C

gather data from documentary and oral sources.

D

25.Basal body temperature refers to the most lowest temperature of a healthy

A B C

individual during waking hours.

D

26.Research in the United States on acupuncture has focused on it use in pain reliefA B C D

and anesthesia.

27.The Moon's gravitational field cannot keep atmospheric gases from escape into

A B C

space.

D

28.Although the pecan tree is chiefly value for its fruit,its wood is used extensivelyA B C

for flooring,furniture,boxed,and crates.

D