Question

【題目】 (共5小題；每小題2分，滿分10分)

根據(jù)短文內(nèi)容，從短文后的選項中選出能填入空白處的最佳選項。選項中有兩項為多余選項。

As warming continues, scientists warn the oxygen content of oceans across the planet could be more and more reduced, with serious consequences for the future of fish and other sea life.

1 One is the simple fact that as water gets warmer, it can hold less dissolved (溶解的) oxygen. The other reason is less obvious. The entire ocean gets its oxygen from the surface — either from the atmosphere, or from photosynthesizing algae floating at the top of the sea. 2

Global warming is expected to reduce the mixing of the ocean by making surface seawater lighter. That’s because in a warmer world we can expect more rainfall and more melting(融化) of glaciers, icebergs, and ice sheets. 3 The extra heat from the warming atmosphere will also make surface water expand and thus make it lighter still. 4 Instead, more of the oxygen will remain near the surface, where it will be used up by oxygen-breathing organisms.

A low-oxygen ocean may become an inescapable feature of our planet. A team of Danish researchers wondered how long oxygen levels would drop if we could somehow reduce our carbon dioxide emissions to zero by 2100. They determined that over the next few thousand years oxygen levels would continue to fall, until they declined by 30 percent. The oxygen would slowly return to the oceans, but even 100,000 years from now they will not have fully recovered. 5

A. It’s not known why the oxygen level of oceans has reduced.

B. Scientists point to two reasons to expect a drop in ocean oxygen.

C. Fresh water’s inpouring will make the water at the ocean’s surface lighter.

D. The oxygen then spreads to the deep ocean as the surface water slowly sinks.

E. Global warming has caused the reduction of the oxygen content of oceans worldwide.

F. The light surface water will be less likely to sink so the deep ocean will get less oxygen.

G. If they are right, we have every reason to worry about the major effect it has on sea life.

Answer 1

【答案】

【1】B

【2】D

【3】C

【4】F

【5】G

【解析】

【文章大意】本文是說明文。文章簡要介紹了海水中氧氣含量降低的主要原因及其可能對海洋生物帶來的長期的影響。

【1】從文章篇章結(jié)構(gòu)分析，本空為段落主旨句。本段介紹了全球變暖使海洋含氧量降低的原因，并且"One" "The other reason"與B項中的"two reasons"相呼應(yīng)，故選B。

【2】根據(jù)段落主旨和空前的"The entire ocean gets its oxygen from the surface...at the top of the sea"可知，此處是通過說明海洋中氧氣的來源與循環(huán)來解釋海洋含氧量下降的原因的，故D項"然后，隨著表層海水的慢慢下沉，氧氣擴散至海洋深處"符合語境。

【3】根據(jù)空前的內(nèi)容和常識可知，雨水和冰川、冰山及冰原融水都屬于淡水，海洋中的水是咸水，而淡水的密度比咸水的小，因此淡水的注入會使海洋表面的水變得更輕。故C項符合語境。C項中的"make the water... lighter"與下文中的"make it lighter"的對應(yīng)關(guān)系亦是提示。

【4】根據(jù)空前的"The extra heat from the warming atmosphere will..."和空后的"Instead, more of the oxygen will remain..."可知，F(xiàn)項與空前的句子的句式相同，且與空后的句子的內(nèi)容存在語意上的轉(zhuǎn)折關(guān)系，故F項符合語境。

【5】G項中的"they"與上文中的"A team of Danish researchers"相呼應(yīng)，且上文講到即使我們把二氧化碳的排放降低到零，海洋含氧量也需要很長時間才能恢復(fù)，其對海洋生物造成的影響將是長期的，故G項"如果他們是對的，那么我們完全有理由對它對海洋生物的重大影響感到擔(dān)憂"符合語境。