8.The Chisos Mountains in Big Bend National Park in Texas were created by volcanic eruptions that occurred _____.

(A)the area in which dinosaurs roamed

(B)when dinosaurs roamed the area

(C)did dinosaurs roam the area

(D)dinosaurs roaming the area.

9.In bas-relief sculpture,a design projects very slightly from its background,_____ some coins.

(A)as on

(B)because

(C)the way that

(D)similarly.

10.Alaska found the first years of its statehood costly because it had to take over the expense of services _____ previously by the federal government.

(A)To provide

(B)Be provided

(C)providing

(D)provided.

11.With age,the mineral content of human bones decreases,_____ them more fragile.

(A)make

(B)and to make

(C)thereby making

(D)which it makes.

12.Not until Kentucky's Mammoth Cave had been completely explored in 1972_____.

(A)when was its full extent realized(B)that its full extent realized

(C)was its full extent realized

(D)the realization of its full extent.

13.The first explorer _____ California by land was Jedediah Strong Smith,a trapper who crossed the southwestern deserts of the United States in 1826.

(A)that he reached(B)reached

(C)to reach

(D)reaching it