When a caterpillar (毛虫)pretends to be a snake to keep off potential predators (捕食者)，it should probably expect to be treated like one. This is exactly what happened in Costa Rica earlier this year, when researchers witnessed a hummingbird defending its nest from what it interpreted to be a snake, but was actually a caterpillar, which was feeding on a leaf above the nest.
These caterpillars resemble flat dried leaves as adults. They can expand the top of their heads to expose a pair of eyespots that discourage potential predators. When disturbed, they raise their head up and move from side to side, increasing the snake-like appearance. In particular they resemble a green parrot snake, known to feed on nesting birds.
Hummingbirds have a few styles of flying: visiting flowers, feeding on some tiny insects, chasing each other， and mating territory (领土)display flights. Mobbing (围攻)behavior directed against a threat to their nest is much less common but easy to recognize if you know their flight behaviors.
The interaction of the caterpillar and the humming birds took place in Costa Rica. The comings and goings of the female hummingbird around its nest may have disturbed the caterpillar, causing it to expose its eyespots, which in turn caused the hummingbird to defend its nest using what is referred to as ‘mobbing behavior’ by birds.
The caterpillar was unable to feed during the 26-minutes of nearly continuous attacks. Most of the bird’s movements were cautious, but included quick attacks to peck or bite the eyespots.
It was difficult for either the bird or caterpillar to withdraw from the standoff (僵局)，with the hummingbird protecting its nest and the caterpillar just trying to finish its leafy meal. Eventually the caterpillar gave up on eating and crawled away while still under attack, and the hummingbird continued normal nesting behavior.
When birds exhibit this mobbing behavior targeting snaked eyes, it often ends with snakes being killed by repeated bites and pecks near the head. As for creatures that imitate snakes to protect themselves from being eaten, can they in turn protect themselves? Because the hummingbird behavior was typical anti-snake behavior, it can be considered replicable (可复制的).
Future studies of this behavior can be conducted using a tiny, caterpillar robot. It should be remote controlled, light enough to attach to a leaf or stem, and wireless. With such a robot, researchers could vary the eye-like nature and contrast of spots on the head of the robot to test various responses of nest-defending birds. A study like this could definitively test the effects of eye-like versus other imitating patterning for exciting the defensive attacks.
And, it turns out that the caterpillar feeds on a leaf on the same plant, as far away from the nest as possible!
1.What do we know about caterpillars and hummingbirds from the passage?
A. They belong to the same species.
B. They are natural enemies of each other.
C. They are insects and birds respectively.
D. They compete against each other for territory.
2.Hummingbirds will show their mobbing behaviors when visitors____.
A. are picking flowers B. are chasing each other
C. interrupt their eating leaves D. set foot on their territories
3.Why is neither the hummingbird nor the caterpillar willing to withdraw at first?
A. Because the hummingbird is trying to finish its leafy meal.
B. Because the caterpillar is protecting the hummingbird’s nest.
C. Because they behave in this way out of their own interest.
D. Because there is a green parrot snake watching them.
4.A tiny caterpillar robot can be used to____.
A. imitate the anti-snake behavior
B. test nest-defending birds’ responses
C. take control of the snake’s behavior
D. guard against the defensive attacks
Are you having so much of work to finish and are unable to keep your home clean and healthy? Don’t worry. Robotic vacuum cleaners are here to help you in cleaning.
The robotic vacuum cleaners are outfitted with sensors, motherboard, Wi-Fi, and lasers to navigate across the home by themselves. They are made so small that they undoubtedly creep under the furniture, cupboards, beds, carpets and so on to detect and clean the dust. Whereas the robotic vacuum cleaners don’t require any help from you， you just need to set it and then carry on your work such as cooking， painting, office work, etc. as it can efficiently clean without any supervision. If their batteries die off, they will automatically go to the charge station and get charged.
The robotic vacuum cleaners make very little noise when compared to that of the standard vacuum cleaners. To collect all the dirt and grime that has been cleaned, these robotic vacuum cleaners come with a built-in waste bin. You can with no difficulty clean this inbuilt dustbin and can reuse them again and again.
The problematic thing with the standard vacuum cleaner is that the vacuum bags are costly and has to be replaced once in 60 days. That is why it is best to invest your money in purchasing the robotic vacuum cleaner. Its purchase price may be a little high, but once you buy it, the maintenance cost will be decreased with so many other benefits.
There are different types of robotic vacuum cleaners on the market right now in different sizes. Make a wise decision and buy the best robotic vacuum cleaner that can fulfill all your requirements so that you can be happy and hygienic (卫生的).
1.The underlined word “navigate” in Paragraph 2 is closest in meaning to____.
A. plot the path B. reduce noise
C. collect information D. charge the battery
2.The robotic vacuum cleaners beat the standard ones in the following aspects EXCEPT that____.
A. they are cheaper and smaller in size
B. they cost less for maintenance
C. they make less noise when working
D. they are more intelligent and efficient
3.Which of the following best summarizes Paragraphs 2 and 3?
A. The original design of robotic vacuum cleaners.
B. The technical theory of robotic vacuum cleaners.
C. The features of robotic vacuum cleaners.
D. The functions of robotic vacuum cleaners.
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1.What is the selling point of the Urban Blue?
A. It was made when Nixon was in office.
B. It is the most precise watch in the world.
C. It is designed by the company's own engineers.
D. It is high in quality but amazingly low in price.
2.To guarantee customers’ satisfaction，the watch producer promises that .
A. they will reduce the engineering time in the future
B. they will sell the watch always at a price of $29
C. customers can wear the watch on trial for 3 months
D. customers can return the watch for a full refund within 30 days
After graduation, Susan was asked to become the executive director of the Floating Hospital. She __ at first, as it was a very big job and she didn’t know if she could __it. But finally, she __.While her job was rewarding, she soon got tired of it. When she sat at her desk one day, the __ came into her mind to go down to the New School for Social Research.__she was learning to trust her intuition (直觉)，she decided to have a go.
Without any forethought, she titled the __ ‘Feel the Fear and Do It Anyway’. Susan was __ as she faced the first session of the twelve-week course. The two hours went well, but she then was challenged with a __ fear, for she didn’t know what to teach the next week. But every week she found she had more to say. And her __ level grew. She realized she had learned so much over the years about __ fear. And her students were drinking it up. At the end of the course, they were __ at how shifting their thinking really changed their lives.
Susan __ decided to write a book based on the course she had taught. She faced many roadblocks. And after four agents and fifteen __from various publishers, she __ put the proposal in a drawer.
After three years of writing, she was going through the drawer that __her much-rejected book proposal. Picking it up, she had a(n) __ sense that she held something in her hands that many people __ to read. So, she set out with much __ to find a publisher who believed in her book the __ way she did. This time, she succeeded. She succeeded __ her wildest dreams.
She was so happy she followed her heart and never gave up overcoming fears that stood in her way.
1.A. admitted B. wondered C. hesitated D. recognized
2.A. help B. handle C. hatch D. have
3.A. explained B. paused C. ignored D. agreed
4.A. thought B. chance C. approach D. demand
5.A. While B. Since C. If D. Though
6.A. book B. talk C. speech D. course
7.A. nervous B. energetic C. delicate D. depressed
8.A. general B. constant C. pure D. new
9.A. balance B. confidence C. happiness D. success
10.A. handing over B. taking over C. getting over D. looking over
11.A. relieved B. puzzled C. amazed D. amused
12.A. eventually B. gradually C. originally D. temporarily
13.A. rejections B. applications C. indications D. restrictions
14.A. hopefully B. swiftly C. unconsciously D. unwillingly
15.A. held B. emptied C. removed D. supported
16.A. vague B. slight C. acute D. basic
17.A. happened B. afforded C. agreed D. needed
18.A. determination B. hesitation C. satisfaction D. imagination
19.A. right B. ideal C. same D. obvious
20.A. within B. beyond C. behind D. through
---Wow! You look funny in that sweater.
---My grandmother gave it to me for Christmas. You know,____.
A. each bird loves to hear himself sing B. beauty is in the eye of the beholder
C. it is the thought that counts D. the outsider sees the most of the game
The large passenger aircraft C919 AC 101, independently designed and developed by China, turned out to be a huge____ success,
A. controversial B. contradictory C. commercial D. compulsory
