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

(A)does the nucleus hold

(B)the nucleus holding

(C)the nucleus does hold

(D)holds the nucleus

12.The wind-rippled sand at California's Kelso Dunes 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 prestigious that

(B)the most prestigious award

(C)a prestigious award that most

(D)most prestigious award