50. D

【解析】细节理解题。根据最后一段的Scientists have built an early-warning system based on mathematical models. Ideally the system would tell us when to adapt human activities that are pushing an ecosystem toward a breadown or would even allow us to pull an ecosystem bac from the borderline.可知，早期变暖系统发出紧急需要采取预防行动的信号帮助我们维持生态平衡。故选D。 9. 【2019·江苏卷，B】

In the 1960s，while studying the volcanic history of Yellowstone National Par，Bob Christiansen became puled about something that，oddly，had not troubled anyone beforehe couldn't find the par's volcano. It had been nown for a long time that Yellowstone was volcanic in nature — that's what accounted for all its hot springs and other steamy features. But Christiansen couldn't find the Yellowstone volcano anywhere.

Most of us，when we tal about volcanoes，thin of the classic cone(圆锥体)shapes of a Fuji or ilimanjaro，which are created when erupting magma(岩浆)piles up. These can form remarably quicly. In 1943，a Meican farmer was surprised to see smoe rising from a small part of his land. In one wee he was the confused owner of a cone five hundred feet high. Within two years it had topped out at almost fourteen hundred feet and was more than half a mile across. Altogether there are some ten thousand of these volcanoes on Earth，all but a few hundred of them etinct. There is，however，a second les nown type of volcano that doesn't involve mountain building. These are volcanoes so eplosive that they burst open in a single big crac，leaving behind a vast hole，the caldera. Yellowstone obviously was of this second type，but Christiansen couldn't find the caldera anywhere.

Just at this time NASA decided to test some new high-altitude cameras by taing photographs of Yellowstone. A thoughtful official passed on some of the copies to the par authorities on the assumption that they might mae a nice blow-up for one of the visitors' centers. As soon as Christiansen saw the photos，he realied why he had failed to spot the caldera; almost the whole par-2.2 million acres—was caldera. The eplosion had left a hole more than forty miles across—much too huge to be seen from anywhere at ground level. At some time in the past Yellowstone must have blown up with a violence far beyond the scale of anything nown to humans. 58. What puled Christiansen when he was studying Yellowstone？ A. Its complicated geographical features. B. Its ever-lasting influence on tourism. C. The mysterious history of the par. D. The eact location of the volcano.

59. What does the second-paragraph mainly tal about？

A. The shapes of volcanoes. B. The impacts of volcanoes. C. The activities of volcanoes. D. The heights of volcanoes.

60. What does the underlined word \？ A. Hot-air balloon. C. Big photograph.

B. Digital camera. D. Bird's view.

【语篇解读】本文为说明文。讲述了二十世纪六十年代Bob Christiansen在研究黄石公园的火山历史时，奇怪地发现到处看不到火山的影子，原，这儿的火山并不是像我们大部分人想象的那种圆锥体形状的高耸的样子，而是一个巨大的洞，这个洞太大了以至于从地面上的任何地方都看不见。 58.D

【解析】细节理解题。根据第一段最后一句But Christiansen couldn’t find the Yellowstone volcano anywhere.可知，他困惑的是到处看不到火山。故选D。 59.A

【解析】主旨大意题。本段讲述了两种形状的火山，一种是通常人们所理解的由火山岩浆堆积形成的圆锥体，还有一种极具爆发力的火山，它们会在一个大裂缝中爆裂，留下一个巨大的洞，故选A。 60.C

【解析】词义猜测题。根据第三段第一句Just at this time NASA decided to test some new high-altitude cameras by taing photographs of Yellowstone. A thoughtful official passed on some of the copies to the par authorities on the assumption that they might mae a nice blow-up for one of the visitors’ centers.可知，美国国家航空和宇宙航行局为测试一些新的高海拔照相机而拍摄了黄石公园的照片。一位深思熟虑的官员把其中的一些照片副本转交给了公园管理部门，认为他们可能会将其放大以供一个游客中心展示。故可知，此处意为将照片放大，选C。

10. 【2019·浙江卷，C】

California has lost half its big trees since the 1930s, according to a study to be published Tuesday and climate change seems to be a major factor(因素).

The number of trees larger than two feet across has declined by 50 percent on more than 46, 000 square miles of California forests, the new study finds. No area was spared or unaffected, from the foggy northern coast to the Sierra Nevada Mountains to the San Gabriels above Los Angeles. In the Sierra high country, the number of big trees has fallen by more than 55 percent; in parts of southern California the decline was nearly 75 percent.

Many factors contributed to the decline, said Patric Mclntyre, an ecologist who was the lead author of the study. Woodcutters targeted big trees. Housing development pushed into the woods. Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources(资).

But in comparing a study of California forests done in the 1920s and 1930s with another one between 2001 and 2010, Mclntyre and his colleagues documented a widespread death of big trees that was evident even in wildlands protected from woodcutting or development.

The loss of big trees was greatest in areas where trees had suffered the greatest water shortage. The researchers figured out water stress with a computer model that calculated how much water trees were getting in comparison with how much they needed, taing into account such things as rainfall, air temperature, dampness of soil, and the timing of snowmelt(融雪).

Since the 1930s, Mclntyre said, the biggest factors driving up water stress in the state have been rising temperatures, which cause trees to lose more water to the air, and earlier snowmelt, which reduces the water supply available to trees during the dry season. 27. What is the second paragraph mainly about? A. The seriousness of big-tree loss in California. B. The increasing variety of California big trees. C. The distribution of big trees in California forests. D. The influence of farming on big trees in California.

28. Which of the following is well-intentioned but may be bad for big trees? A. Ecological studies of forests. B. Banning woodcutting. C. Limiting housing development. D. Fire control measures.

29. What is a major cause of the water shortage according to Mclntyre? A. Inadequate snowmelt. C. A warmer climate.

30. What can be a suitable title for the tet?

A. California's Forests Where Have All the Big Trees Gone? B. Cutting of Big Trees to Be Prohibited in California Soon C. Why Are the Big Trees Important to California Forests?

B. A longer dry season. D. Dampness of the air.

D. Patric Mclntyre Grow More Big Trees in California

【语篇解读】本文为说明文，根据一项研究表明，自20世纪30年代以，加州已经失去了一半的大树，气候变化似乎是其主要因素。 27.A

主旨大意题。在第二段中，作者用具体数据说明了大树损失在各个地区的严重程度，没有任何地区幸免或不受影响，故选A。 28. D

【解析】推理判断题。根据第三段最后一句Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources（资）.可知，野火控制在控制了森林大火的同时，使得加利福尼亚的森林里挤满了小树，它们与大树争夺资，这对大树产生了不利的影响，故选D。 29.C

【解析】细节理解题。根据最后一段the biggest factors driving up water stress in the state have been rising temperatures, …, and earlier snowmelt, …可知，造成加州水资短缺的最大因素是气温的上升，以及较早的融雪，故选C。 30.A

【解析】主旨大意题。通读全文可知，自20世纪30年代以，加州已经失去了一半的大树，文章分析了引起该现象的几个主要因素。全文围绕“加州森林的大树都去哪儿了”话题展开，故选项A符合题意。

二、2018年高考真题

1.【2018·全国卷I，D】

We may thin we’re a culture that gets rid of our worn technology at the first sight of something shiny and new, but a new study shows that we eep using our old devices (装置) well after they go out of style. That’s bad news for the environment – and our wallets – as these outdated devices consume much more energy than the newer ones that do the same things.

To figure out how much power these devices are using, Callie Babbitt and her colleagues at the Rochester Institute of Technology in New Yor traced the environmental costs for each product throughout its life – from when its minerals are mined to when we stop using the device. This method provided a readout for how home energy use has evolved since the early 1990s. Devices were grouped by generation. Destop computers, basic mobile phones, and bo-set TVs defined 1992. Digital cameras arrived on the scene in 1997. And MP3 players, smart phones, and LCD TVs entered homes in 2002, before tablets and e-readers showed up in 2007.

As we accumulated more devices, however, we didn’t throw out our old ones. “The living-room television is