Question

【題目】 If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation--conversion of liquid water to water vapor. In this manner, the salinity is increased, since the salts stay behind. If this is carried to the extreme, of course, white crystals of salt would be left behind.

The opposite of evaporation is precipitation(降水), such as rain, by which water is added to the ocean. Here the ocean is being diluted(稀釋) so that the salinity is decreased. This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff.

Normally, in tropical regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.

A third process by which salinity may be altered is associated with the formation and melting of sea ice. When seawater is frozen, the dissolved materials are left behind. In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water.

In the Weddell Sea, off Antarctica, the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portions of the oceans of the world.

【1】What is the best title for the passage?

A.Typical Oceans and Their Respective Features

B.The Causes of the Changes in Salinity of Ocean Water

C.Different Oceans Have Different Salinity

D.The Precipitation and Evaporation of Oceans

【2】Which of the following processes will increase salinity of ocean waters?

A.EvaporationB.Precipitation

C.MeltingD.Dilution

【3】According to this passage, the sea ________ is likely to have the lowest salinity.

A.in tropical areasB.off Antarctica

C.of high rainfallD.with abundant

【4】The Weddell Sea _______.

A.is an example of increased salinity in freezing sea water

B.is much larger in area than the Arctic oceans

C.has a much lower salinity now than ever

D.has the denser water in its upper parts

Answer 1

【答案】

【1】B

【2】A

【3】C

【4】A

【解析】

本文是一篇說(shuō)明文，介紹了造成海水鹽度變化的原因。

【1】主旨大意題。通讀全文，特別是根據(jù)第一段中的“There are three basic processes that cause a change in oceanic salinity.”可知，造成海洋鹽度變化的基本過(guò)程有三個(gè)。所以本文主要介紹了造成海水鹽度變化的原因，故短文的最佳標(biāo)題為“海水鹽度變化的原因”。故B項(xiàng)正確。

【2】細(xì)節(jié)理解題。根據(jù)第二段中的“Thus salinity may be increased by the subtraction of water by evaporation”可知，因此，鹽度可以通過(guò)蒸發(fā)減少水分來(lái)增加。所以蒸發(fā)會(huì)使海水鹽度增加，故A項(xiàng)正確。

【3】推理判斷題。根據(jù)第二段中的“The opposite of evaporation is precipitation(降水), such as rain, by which water is added to the ocean. Here the ocean is being diluted(稀釋) so that the salinity is decreased.”可知，降水會(huì)使海水的鹽度降低，因此，降雨量大的海水的鹽度可能最低，故C項(xiàng)正確。

【4】細(xì)節(jié)理解題。根據(jù)最后一段中的“In the Weddell Sea, off Antarctica, the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water.”可知，在南極洲邊緣的威德?tīng)柡Ｖ校�結(jié)冰過(guò)程增加低溫海水的鹽度，從而形成了濃度最大的海水，由此可知，威德?tīng)柡Ｊ呛Ｋ�結(jié)冰時(shí)鹽度增加的一個(gè)例子，故A項(xiàng)正確。

主旨大意題的難度較大，對(duì)文章主題句的把握是關(guān)鍵，科普類說(shuō)明文一般第一段就會(huì)點(diǎn)明主題，例如本篇第1題，通讀全文，特別是根據(jù)第一段中的“There are three basic processes that cause a change in oceanic salinity.”可知，造成海洋鹽度變化的基本過(guò)程有三個(gè)，由此可知，本文主要介紹的是造成海水鹽度變化的原因，故短文的最佳標(biāo)題為“海水鹽度變化的原因”。故B項(xiàng)正確。