1 . Scientists have discovered how plants manage to live alongside each other in places that are dark and shady. Plants in the deep darkness of a thick forest, where natural supplies are not very great in amount, won’t attempt to top their neighbors in growth as those in moderate (中度的) shade do. In deep shade conditions, it would be a waste of energy and harmful to survival because green shoots would never be able to top their larger neighbors in growth.

So how do plants prevent such growth in deep shade conditions? The secret lies in the clocks insides them, say scientists from the John Ines Centre and the University of Bristol.

They have discovered that when plants notice deep shade, this changes the expression of genes parts of the circadian clock (昼夜节律时钟) — the inner daily timer found in plants and other things. These clock parts perform an additional role in preventing plants from lengthening and overtopping neighbors.

The work identifies a previously unknown role of the circadian clock in controlling plant development and the findings may have possible effects on both natural plant populations and crops. Professor Antony Dodd of the John Innes Centre said, “The biological clock of plants plays a big part in their development and fitness. This work casts new light on a new role of the circadian clock in adapting plants to competition with other plants in their environments.” “It also gives us new insights into how plants adapt to very deep shade, where resources are very limited,” said Professor Kerry Franklin at the University of Bristol.

This work provides evidence for the firmness of the circadian clock in stressful environments, and information that may be useful in developing new generations of crops in a challenging climate.

1. What do plants normally do in moderate shade?

A．Struggle to preserve energy.	B．Compete for limited resources.
C．Try to outgrow their neighbors.	D．Depend on each other to survive.

2. How does the circadian clock affect plants?

A．By changing their gene expression.	B．By making them realize light change.
C．By helping them adapt to the darkness.	D．By controlling their growth in deep shade.

3. Why does the author write the text?

A．To share a new discovery about plants.	B．To introduce the role of the circadian clock.
C．To explain plants secret of living in forests.	D．To compare plants living in certain condition.

4. What is the best title for the text?

A．How plants face a challenging climate

B．Why plants respond to different shade levels

C．Why the circadian clock is vital to plants' growth

D．How plants become good neighbors in times of stress

2 . A wildfire kills most things in its path, but despite the flames and intense temperatures, rarely is everything reduced to ashes -and that plays a key role in a forest's regeneration. Just one year after the fire, the survivors dominate the forest, and grasses replace the burnt ground. Wildflowers are abundant bushes and small trees have started to grow, and Jack Pine returned. So, it's an amazing ecological system of creating new forest life when it appears that all is lost, one that has evolved throughout the ages, where fire has always played a vital role.

What does the underlined word "one" in the last paragraph refer to?

A．A fire.

B．A life

C．A time.

D．A system

3 . Early last summer, I bought some yam（山药）roots for food but days later, a tuber （块茎）left was sprouting（发芽）. Thinking it was a waste of money to throw it away, I _____ the tuber into a flower pot hoping that it might take root and ______ something that could be put on the dinner table.

In the following months, I ____ the tuber regularly. Thankfully, the _____ yam grew well. Soon it was autumn, and I decided to ______ .

I pulled out the leaves of the yam and began to dig with my fingers carefully for I knew the yam could ______easily. Suddenly my fingers __ the yam root. When almost no __ was left, I tried to pull the root but failed.

In ______   , I turned the pot over. Half of the yam root had grown through one of the three holes ______

The whole tuber, _____ two parts, one in and one out of the pot, was in the _____ of a handwritten L. Unlike ordinary yam roots, the part outside the pot was not round—it was _____ , looking like a hand of an old farmer who works hard to make a ______ . The very end of the part outside the pot was _____ . Obviously, the skin must have been rubbed off during its __ with the heavy pot. The very tip of the unusual part seemed to be bleeding.

The sight filled me with ______ . Then and there my opinion of the plant _____ . I came to understand that the tuber, though ______ wounded, had struggled hard. Such was a yam, an ordinary-looking plant with ________characteristics.

1.

A．cooked

B．ruined

C．buried

D．cut

2.

A．remove

B．produce

C．replace

D．protect

3.

A．bought

B．threw

C．watered

D．ate

4.

A．abandoned

B．forgotten

C．injured

D．potted

5.

A．perform

B．attempt

C．harvest

D．withdraw

6.

A．stand

B．grow

C．fall

D．break

7.

A．touched

B．pulled

C．crashed

D．killed

8.

A．earth

B．root

C．air

D．plant

9.

A．excitement

B．shame

C．puzzlement

D．terror

10.

A．in the sky

B．on the top

C．in the bottom

D．under the ground

11.

A．picking out

B．consisting of

C．giving away

D．taking down

12.

A．color

B．form

C．voice

D．size

13.

A．flat

B．long

C．rough

D．weak

14.

A．choice

B．contribution

C．wish

D．living

15.

A．skinless

B．endless

C．useless

D．stainless

16.

A．negotiation

B．struggle

C．cooperation

D．relationship

17.

A．victory

B．regret

C．envy

D．respect

18.

A．strengthened

B．changed

C．disappeared

D．remained

19.

A．barely

B．temporarily

C．purposefully

D．seriously

20.

A．tough

B．steady

C．common

D．gentle

4 . The Greenwood fire took its name from the nearby lake where lightning struck on Aug.15, causing a wildfire that burned for weeks. Fueled by drought and wind, its persistence dominated headlines for much of late summer and early fall in Minnesota. When the last flames were finally put out, the northern Minnesota fire had consumed nearly 27,000 acres, countless firefighting resources, and at its worst, the lives that some had built around nearby McDougal Lake. Vast areas of forest were left burned-out, with the black and bare remains of what were once massive pines.

But, despite the destruction left behind, Mother Nature is set to a comeback. When organic matter is burned from the forest floor, seeds dropped by plants and trees begin to take hold, with the sprouting species emerging first. The trees above have died, which sends a chemical signal to the root system that is actually more expansive than just under that tree, and that chemical response encourages those root systems to re-grow. Ten years ago, a fire ripped through 93,000 acres of Minnesota forest in and around the BWCA. Today, that burnt area's rebirth is well underway.

"Here in the Pagami Creek wildfire scar, we have Jack Pine, Red Pine, Black Spruce, Aspen and paper birch-those are our main species, those are the ones that are growing quickly. It's 10 years on, and these trees are 10 to 15 feet tall in many areas," said Kyle Stover from the U.S. Forest Service.

A wildfire kills most things in its path, but despite the flames and intense temperatures, rarely is everything reduced to ashes -and that plays a key role in a forest's regeneration. Just one year after the fire, the survivors dominate the forest, and grasses replace the burnt ground. Wildflowers are abundant bushes and small trees have started to grow, and Jack Pine returned. So, it's an amazing ecological system of creating new forest life when it appears that all is lost, one that has evolved throughout the ages, where fire has always played a vital role.

1. What can we learn about the Greenwood fire?

A．It was a natural occurrence	B．It was caused by drought.
C．it gained half-year fame.	D．It took many people's lives.

2. What happens to the burnt area after the fire?

A．Seeding growth is held up.	B．Burnt organic matter hardly functions.
C．Root systems spread further and wider	D．Chemicals in the soil are in greater demand.

3. What can we say about the trees and plants in Minnesota?

A．They are flammable	B．They are fire-resistant
C．They are fire-adapted.	D．They are overgrown.

4. What does the underlined word "one" in the last paragraph refer to?

A．A fire.

B．A life

C．A time.

D．A system

5 . 阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。

As the world    1    （large）cotton consumer and the second largest producer of cotton, China has a long history of cotton cultivation. It is worth    2    （mention）that Xinjiang cotton is highly regarded because of its high yield and high quality.

    3    （locate）in the inland of Eurasia（欧亚大陆）, Xinjiang has a typical mild continental climate. Drought, little rain, sufficient heat, big temperature    4    （different）between day and night and long day make a good growth environment for cotton.

Though Xinjiang has little rainfall, it has a large number of snow-capped mountains, from which meltwater gives cotton abundant water resource. Meanwhile,    5    contrast to the instable rainfall in the monsoon（季风）regions, mountain snowmelt has the characteristics of stable water transportation,    6    is very suitable for the growth of cotton.

Xinjiang is lightly populated and has a vast planting area. It has    7    area of 1.66 million square kilometers and a population of about 23 million. The cotton planting area    8    （cover）25,019.3 square kilometers in 2020，according to the Department of Agriculture and Rural Affairs of Xinjiang.

The combination of advantaged    9    （nature）conditions and mechanical technology makes Xinjiang cotton have good quality. Endless white cotton has also become one of the    10    （symbol）of great beauty in Xinjiang.