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
