Question

【题目】 (共5小题；每小题2分，满分10分)

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

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】本文是说明文。文章简要介绍了海水中氧气含量降低的主要原因及其可能对海洋生物带来的长期的影响。

【1】从文章篇章结构分析，本空为段落主旨句。本段介绍了全球变暖使海洋含氧量降低的原因，并且"One" "The other reason"与B项中的"two reasons"相呼应，故选B。

【2】根据段落主旨和空前的"The entire ocean gets its oxygen from the surface...at the top of the sea"可知，此处是通过说明海洋中氧气的来源与循环来解释海洋含氧量下降的原因的，故D项"然后，随着表层海水的慢慢下沉，氧气扩散至海洋深处"符合语境。

【3】根据空前的内容和常识可知，雨水和冰川、冰山及冰原融水都属于淡水，海洋中的水是咸水，而淡水的密度比咸水的小，因此淡水的注入会使海洋表面的水变得更轻。故C项符合语境。C项中的"make the water... lighter"与下文中的"make it lighter"的对应关系亦是提示。

【4】根据空前的"The extra heat from the warming atmosphere will..."和空后的"Instead, more of the oxygen will remain..."可知，F项与空前的句子的句式相同，且与空后的句子的内容存在语意上的转折关系，故F项符合语境。

【5】G项中的"they"与上文中的"A team of Danish researchers"相呼应，且上文讲到即使我们把二氧化碳的排放降低到零，海洋含氧量也需要很长时间才能恢复，其对海洋生物造成的影响将是长期的，故G项"如果他们是对的，那么我们完全有理由对它对海洋生物的重大影响感到担忧"符合语境。