11.Not only _____ all the positive charge of an atom,it is also the site of the weight of every atom.

(A)does the nucleus¹ hold

(B)the nucleus holding

(C)the nucleus does hold

(D)holds the nucleus

12.The wind-rippled sand at California's Kelso Dunes² resembles _____.

(A)to be an ocean floor

(B)as an ocean floor

(C)an ocean floor

(D)being an ocean floor

13.Fossil records indicate _____ existing in the past have become extinct.

(A)that many species of organisms

(B)many species of organisms that

(C)many species of organisms are

(D)there are many organisms

14.Experiments related to the sense of smell are more easily _____ than those related to perception of color.

(A)setting them up

(B)to set up

(C)set up

(D)sets up those

15.The Pulitzer Prize has been _____ in American literature for more than seventy years.

(A)the award most prestigious³ that

(B)the most prestigious award

(C)a prestigious award that most

(D)most prestigious award

16.Those interested in covered bridges can find six of they between Keene and

A B C D

Winchester,New Hampshire.

17.The Sun's energy is generated deep in the solar core by the synthesis of helium

A B C

from hydrogen through a sequences of thermonuclear fusion⁴ reactions.

D

18.Using carbon-dating techniques,archaeologists can determine the age of manyA

ancient objects by measurement the amount of radioactive carbon they contain.

B C D

19.The evolutionary⁵ adaptation of a particular species of animal over time occurs in

A B

response to environmental conditions,including others animals.

C D

20.Saturn⁶ is the second largest planet after Jupiter,with a diameter nearly ten times

A B C

those of Earth.

D