2014年下半年大学英语四级考试阅读提升训练（九）

　　大学英语四级阅读理解练习九

　　Directions: There are 4 passages in this part. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A), B), C) and D). You should decide on the best choice and mark the corresponding letter on the Answer Sheet with a single line through the centre.

　　Questions 1 to 5 are based on the following passage:

　　Water on the earth is being recycled continuously in a process known as the hydrologic cycle (水循环). The first step of the cycle is the evaporation of water in the oceans. Evaporation is the process of water turning into vapor, which then forms clouds in the sky. The second step is the water returning to the earth in the form of precipitation (降水) ：either rain, snow or ice. When the water returning to the earth's surface, it runs off into the rivers, lakes, and the ocean, where the cycle begins again.

　　Not all water, however, stays on the surface of the earth in the hydrologic cycle. Some of it sinks slowly into the ground through infiltration (渗透) and collects under the earth's surface as groundwater. This groundwater is extremely important to life on earth, since 95 percent of the earth's water is in the oceans and is too salty for human beings or plants. Of the 5 percent on land, only .05 percent is above ground in rivers or lakes. The rest is underground water. This underground water is plentiful and dependable, because it doesn't depend on seasonal rain or snow. It is the major source of water for many cities. But as the population increases and the need for water also increases, the groundwater in some areas is getting dangerously low. Added to this problem is an increasing amount of pollution that sinks into the groundwater through infiltration. In the future, with a growing population and more poisonous waste, the hydrologic cycle we depend on could become dangerously unbalanced.

　　1. The first paragraph of this passage tells about ________.

　　A) the cycling of earth's water

　　B) the evaporation of ocean water

　　C) the formation of clouds

　　D) the sources of river, lake and sea

　　2. Water returns to the earth by _________.

　　A) infiltration

　　B) precipitation

　　C) pollution

　　D) evaporation

　　3. The earth's groundwater __________.

　　A) depends on seasonal rain

　　B) is .05 percent of all water

　　C) comes from polluted waste water

　　D) collects under the earth

　　4. The amount of groundwater is __________.

　　A) about 95 percent of all water

　　B) less than 5 percent of all water

　　C) .05 percent of above-ground water

　　D) 95 percent of above-ground water

　　5. The supply of groundwater is getting low because of _________.

　　A) conservation

　　B) poisonous waste

　　C) pollution

　　D) population increase