单选题 Volcanoes are the ultimate earth-moving machinery. Eruptions have rifted continents, raised mountain chains, constructed islands and shaped the topography of the earth. The entire ocean floor has a basement of volcanic basalt.
Volcanoes have not only made the continents, they are also thought to have made the world's first stable atmosphere and provided all the water for the oceans, rivers and ice-caps. There are now about 600 active volcanoes. Every year they add two or three cubic kilometers of rock to the continents. Imagine a similar number of volcanoes smoking away for the last 3,500 million years. That is enough rock to explain the continental crust.
What comes out of volcanic craters is mostly gas. More than 90% of this gas is water vapor from the deep earth: enough to explain, over 3,500 million years, the water in the oceans. The rest of the gas is nitrogen, carbon dioxide, sulphur dioxide, methane, ammonia and hydrogen. The quantity of these gases, again multiplied over 3,500 million years, is enough to explain the mass of the world's atmosphere. We are alive because volcanoes provided the soil, air and water we need.
Geologists consider the earth as having a molten core, surrounded by a semi-molten mantle and a brittle, outer skin. It helps to think of a soft-boiled egg with a runny yolk, a firm but squishy white and a hard shell. If the shell is even slightly cracked during boiling, the white material bubbles out and sets like a tiny mountain chain over the crack—like an archipelago of volcanic islands such as the Hawaiian Islands. But the earth is so much bigger and the mantle below is so much hotter.
Even though the mantle rocks are kept solid by overlying pressure, they can still slowly 'flow' like thick treacle. The flow, thought to be in the form of convection currents, is powerful enough to fracture the 'eggshell' of the crust into plates, and keep them bumping and grinding against each other, or even overlapping, at the rate of a few centimeters a year. These fracture zones, where the collisions occur, are where earthquakes happen. And, very often, volcanoes.

单选题 Why volcanoes are both significant to the globe and to human beings?

【正确答案】 B

【答案解析】推断题。题干问火山对于世界和人类的意义，文章第一段列举对地球地形的影响，如举起山脉、建构岛屿。第二段首句为主题句，即Volcanoes have not only made the continents...atmosphere...water。第三段最后一句We are alive because volcanoes provided the soil, air and water we need. 表明了对人类的影响。综合来看，答案为B，即火山创造了大陆、空气、水。

单选题 What accounts for a large proportion among those things which volcanic craters bring out?

【正确答案】 B

【答案解析】细节题。原文第三段第一句What comes out of volcanic craters is mostly gas. (从火山喷发出来的主要是气体。)mostly(大多)对应account for a large proportion(占较大比例)。其余三个选项均为干扰项，水和土壤占据的比例较小，火山喷发并不是导致海洋形成的直接原因，它只是提供了海洋形成需要的水资源。

单选题 What rhetorical device does the writer used to describe earth?

【正确答案】 C

【答案解析】推断题。题干问，作者在描写火山时，用了什么修辞手法?原文第四段，关键词soft-boiled egg，作者将地球比作鸡蛋，有一层脆的外壳，地幔如蛋清，其核心如蛋黄。可知，应选comparison(对比)，尤其指相同之处的对比。选项A，contrast也为对比之意，但指的是不同之处的对比。选项B意为夸张，D意为拟人，均不符合原文。

单选题 Where do volcanoes and earthquakes often occur?

单选题 Which of the following is mentioned according to the passage?

【正确答案】 D

【答案解析】细节题。此题应用排除法，选项A，火山的不同类型，很明显，文章并没有提及。选项B，预测火山喷发所做出的努力，也没有提及。选项C，火山喷发带来的灾害，文章讲到其给地球与人类带来的益处，并没有讲负面的影响，故排除。选项D，火山喷发的原因，文章后两段将地球比作鸡蛋，形象地描述了火山喷发的原因，故选D。