单选题
1 The dominant feature on the map of Canada is the two-million-square-mile mass of ancient rock known as the Canadian Shield. The shield sweeps in a great arc around Hudson Bay from far northwest to far northeast, touching the Great Lakes on the south and extending eastward deep into Quebec. The rock of the shield consists mainly of granite and gneiss formed nearly four billion years ago. During the ice ages, huge glaciers advanced and retreated over the region, scouring the surface, removing most of the existing soil, and hollowing out countless lakes. 2 Clay soils exist in a few areas on the shield's southern edge, but attempts to bring them into agricultural use have been largely unsuccessful. However, the region's mineral wealth has sustained both temporary and permanent settlements during the past century, and more recently, some of its vast potential for hydroelectric power has been tapped.
单选题
The word scouring in paragraph 1 is closest in meaning to
【正确答案】
D
【答案解析】Scouring means scraping in this context. Clues: ...removing most of the existing soil, and hollowing out countless lakes.
单选题
The word sustained in paragraph 2 is closest in meaning to
【正确答案】
C
【答案解析】Sustained means supported in this context. Clues: ...attempts to bring them into agricultural use have been largely unsuccessful. However, the region's mineral wealth both temporary and permanent settlements...; the prefix sus- = under.