1 . Directions: Fill in each blank with a proper word chosen from the box. Each word can be used only once. Note that there is one word more than you need.

A. adaptable        B. classic          C. determined   D. effectively   E. fundamentally F. immediately     G. sideways       H. stretched       I. survival        J. underside       K. upright

Why Are Trees Tree-shaped?

While running through a leafy park days ago, I passed dozens of tree species of different sizes and ages, and I was suddenly struck by how     1     similar they were. Wide trunks split into smaller branches in the same sort of way. You could guess the height of a tree just by looking at how wide its trunk is. We would notice     2     if someone drew a tree with branches that were too wide or a trunk that was too thin. What makes a tree look like a tree? Maximising the sunlight hitting the tree’s leaves is obviously critical for the tree’s     3    . But the size and shape of the branches is largely     4     by a different standards: a tree must be strong enough to stay standing     5    , possibly for centuries. Imagine an oak tree, with branches reaching     6     off the main trunk. Each branch has to support its own considerable weight, so the wood in its lower half is slightly compressed and the top half is being     7    . That top layer of a branch takes the weight of the branch. And a particular type of wood has grown there to do that job. It’s called reaction wood, because it formed as reinforcement (增强) to take the increasing weight as the branch grew. The trees that reinforce on top the branches are the “lollipop” ones:     8     branching species like oaks. But there is another way of solving that problem. Some trees grow their reinforcing reaction wood on the     9     instead, so the branch is pushed up, rather than pulled from above. It works, but not as     10    , so these trees can’t support large side branches. The ones that reinforce underneath have a thick trunk with much smaller side branches, and they grow to be conical—some examples of these trees are pines and firs.

oak pine fir

2 . Directions: Fill in each blank with a proper word chosen from the box. Each word can be used only once. Note that there is one word more than you need.

A. removed; B. guaranteed; C. quality; D. ranks                 E. threats; F. access; G. long-term; H. unproductive        I. effective; J. overlooking; K. characterize

Coffee’s Climate Crisis

Howard Schultz wants to know if I drink coffee. The Starbucks boss is sitting on a balcony     1     the company’s leafy farm in the Costa Rican province of Alajuela, where I’m told the coffee — harvested and roasted on-site — is a must-try. Like more than 60% of Americans, I drink coffee at least once a day. The Costa Rican blend Schultz pours me has a special taste that mixes citrus and chocolate flavors.

But the future of my cup of Costa Rican Arabica is not     2    , Schultz says. After nearly four decades at Starbucks, he is leaving at the end of June, and in the role of executive chairman for almost 15 months, he has been looking past Starbucks’ day-to-day operations to its     3     challenges and opportunities. Climate change     4     high among them. As temperatures rise and droughts intensify, good coffee will become increasingly difficult to grow and expensive to buy. Since governments are reacting slowly to the problem, companies like Starbucks have stepped in to save themselves, reaching to the bottom of their supply chains to ensure reliable     5     to their product. “Make no mistake,” Schultz tells me, “climate change is going to play a bigger role in affecting the     6     and integrity of coffee.”

This farm, with its verdant vistas and a trickling waterfall, seems far     7     from the rising sea levels, unbearable heat and destructive storms that     8     climate change. But global warming is exactly why Starbucks bought the 600-acre plot in 2013, and why Schultz makes the 3,500-mile trip from Seattle a few times a year as he has done on this March day. The farm is Starbucks’ field laboratory into the     9     posed to coffee by climate change and its testing facility for how it can adapt to the challenge. Schultz hopes that the research here will inform agricultural practices for millions of farmers across the globe, including the ones that supply the company. “We have to be in the soil, growing coffee, to understand firsthand how to fix the situation,” he says. Study after study has laid out the threat climate change poses to the coffee industry. Rising temperatures will bring drought, increase the range of diseases and kill large swaths of the insects that pollinate coffee plants. About half of the land around the world currently used to produce high-quality coffee could be     10     by 2050, according to a recent study in the journal Climatic Change.

3 . Directions: Fill in each blank with a proper word chosen from the box. Each word can only be used once. Note that there is one word more than you need.

A. extended     B. tasty       C. reserve            D. resistant          E. pause          F. consume G. slows        H. supplies     I. associated       J. properties        K. tapping

Extreme conditions produce extremely tough plants. The big difference between "drought—tolerant" plants and these tough plants: metabolism. Many different kinds of plants have developed tactics to weather dry spells. Some plants     1     of water to see them through a drought; others send roots deep down to subsurface water supplies. But once these plants use up their stored water or tap out the underground supply, they cease growing and start to die. They may be able to handle a drought of some length, and many people use the term "drought tolerant" to describe such plants, but they never actually stop needing to     2     water, so Farrant prefers to call them drought     3    .

Resurrection plants, defined as those capable of recovering from holding less than 0.1 grams of water per gram of dry mass, are different. They lack water—storing structures, and their existence on rock faces prevents them from     4     groundwater, so they instead developed the ability to change their metabolism. When they detect a/an       5     dry period, they change their metabolisms, producing sugars and certain stress—     6     proteins and other materials in their tissues. As the plant dries, these resources take on first the     7     of honey, then rubber, and finally enter a glass—like state that is "the most stable state that the plant can maintain," Farrant says. That     8     the plant's metabolism and protects its dried—out tissues. The plants also change shape, shrinking to minimize the surface area through which their remaining water might evaporate. They can recover from months and years without water, depending on the species.

What else can do this dry—out—and—revive trick? Seeds—almost all of them. At the start of her career, Farrant studied seeds such as avocados(牛油果) , coffee and lychee(荔枝). Though     9    , such seeds are delicate — they cannot bud and grow if they dry out. Most seeds can wait out the dry, unwelcoming seasons until conditions are right and they sprout. Yet once they start growing, such plants seem not to retain the ability to hit the     10     button on metabolism in their stems or leaves.

4 . Directions:Complete the following sentences by using the proper form of the words or expressions   given in the frame.Each one can only be used once.

A. capable        B. effectiveness       C. employing        D.exposure          E.famously           F. joining          G. limitation        H. minimal       I.precisely        J.recognizing       K.worthwhile

Clean Air Act

The air in modern homes and offices is pretty clean,but not as clean as it might be.Often it contains small amounts of volatile(挥发性的）,poisonous,organic compounds.Long-term    1     to these is a bad thing,so clearing them out of the air people breathe is widely accepted as     2    

Finding an effective way to do so has proved difficult.But Stuart Strand, Long Zhang and Ryan Routsong, of the University of Washington,in Seattle,think they have succeeded,As they report in Environmental Science and Technology, their method involves     3     a gene from a rabbit into a popular indoor plant nicknamed Devil's vine—a type of ivy hat is so called because it is    4     difficult to kill.

The idea of     5     plants to de- pollute   the atmosphere inside buildings has been around for decades-but has met with only qualified success. One experiment involving unmodified spider plants,for example,showed that they are indeed     6     of removing formaldhyde (甲醛) from the air.The     7     is that to make much of a difference in a space as large as a house would require turning most of the rooms into spider-plant forests.

Dr Strand, Dr Zhang and Mr Routsong thus sought something suitably transgenic ( 转 基 因 的),but that does not flower indoors. The plant they settled on was Devil's vine,     8     because of its toughness.With the help of a bacterium,they were able to ferry the rabbit version of the gene into the plant's chromosomes(染色 体),and thus to,engineer a type of Devil's vine able to produce an air-cleaning substance. To test the     9     of their idea, the researchers put their modified ivy to work inside greenhouses filled with air containing high levels of harmful substances.The plants performed well,reducing the harmful substances in air to     10    .