Do scientists know how many cryptic species exist?A．Not yet.B．Yes, they do.C．They will know the answer in another one or two years.D．They will never know the answer.
Do scientists know how many cryptic species exist?
A．Not yet.
B．Yes, they do.
C．They will know the answer in another one or two years.
D．They will never know the answer.
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"Hidden" Species May Be Surprisingly CommonCryptic species animals that appear identical but are genetically quite distant—may be much more widespread than previously thought. The findings could have major implications in areas ranging from biodiversity estimates and wildlife management, to our understanding of infectious diseases and evolution.Reports of cryptic species have increased dramatically over the past two decades with the advent of relatively inexpensive DNA sequencing technology. Markus Pfenninger and Klaus Schwenk, of the Goethe-Universitat, in Frankfurt, Germany, analyzed all known data on cryptic animal species and discovered that they are found in equal proportions throughout all major branches of the animal kingdom and occur in equal numbers in all biogeographieal regions.Scientists had previously speculated that cryptic species were predominantly found in insects and reptiles, and were more likely to occur in tropical rather than temperate regions. "Species that are seemingly widespread and abundant could in reality be many different cryptic species that have low populations and are highly endangered. " Says Pfenninger. Until the genetic information of all species in at least one taxon is thoroughly studied, no one will know just how many cryptic species exist. "It could be as high as 30%. " Pfenninger says."I'm extremely surprised by their results. " Says Alex Smith of the University of Guelph in Ontario, Canada. "It's a call to arms to keep doing the broad kind of genetic studies that we are doing. "Sampling as many individuals as possible, scientists hope to complete work on all fish and birds in another 5 to 10 years. Once either of these taxonomic groups is completed, Pfenninger says researchers will be able to decide how many cryptic species exist throughout the animal kingdom.Examples of cryptic species include the African elephant. A 2001 study found the elephants were actually two genetically distinct, non-interbreeding species, the African bush elephant and the African elephant. The species are currently listed as vulnerable and threatened, respectively, by the World Conservation Union (WCU).The reclassifications are more than an academic exercise. They define populations that have evolved independently of each other and whose genetic differences can have significant consequences. In the early 1900s misidentification of mosquito species based on morphology confused attempts to control malaria in Europe. Ultimately, what was thought to be a single species was actually made up of six sibling species, only three of which transmitted the disease. "The basic unit in biology is always the species, and you have to know what you are dealing with. " Pfenninger says. Much previous research is now no longer used, he says, because it is not clear what species was being studied.Which of the following about the significance of the research on cryptic species is NOT true?A．The results of the research can help the development of many other research areas.B．The results of the research can help the development of biodiversity estimates.C．The results of the research can help our understanding of infectious disease evolution.D．The results of the research can help our understanding of "survival of the fittest. "
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Of all the websites, one that has attracted attention recently is my . Most of this attention has come from the hacks is indeed a tough reality, shutting down the site is not the answer. If my shut down, another site would place. Therefore, the right way is to teach teens how to use the site safely and educate them .One of the good way is to change the privacy setting on your profile to “private” actually post their home and school addresses, date of birth, and so on, often predators know exactly where they will be The most information that is safe is your first name and province. Anything more is basically life.Another big problem is photos. I suggest skipping photos and never posting a photo of a friend online without his or her how well you think you know this person. There are no guarantees that they have told the truth.Most of this attention has come from the hacks is indeed a tough reality, shutting down the site is not the answer. {T; F}One of the good way is to change the privacy setting on your profile to “private” actually post their home and school addresses, date of birth, and so on. {T; F}If my shut down, another site would place. Therefore, the right way is to teach teens how to use the site safely and educate them . {T; F}Another big problem is photos. I suggest skipping photos and posting a photo of a friend online without his or her how well you think you know this person. {T; F}There are no guarantees that they have told the truth. {T; F}
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Of all the websites, one that has attracted attention recently is my space.com. Most of this attention has come from the hacks is indeed a tough reality, shutting down the site is not the answer. If my space.com shut down, another site would place. Therefore, the right way is to teach teens how to use the site safely and educate them . One of the good way is to change the privacy setting on your profile to “private” actually post their home and school addresses, date of birth, and so on, often predators know exactly where they will be The most information that is safe is your first name and province. Anything more is basically life. Another big problem is photos. I suggest skipping photos and never posting a photo of a friend online without his or her how well you think you know this person. There are no guarantees that they have told the truth.1. Most of this attention has come from the hacks is indeed a tough reality, shutting down the site is not the answer.2. One of the good way is to change the privacy setting on your profile to “private” actually post their home and school addresses, date of birth, and so on.3. If my space.com shut down, another site would place. Therefore, the right way is to teach teens how to use the site safely and educate them .4. Another big problem is photos. I suggest skipping photos and posting a photo of a friend online without his or her how well you think you know this person.5. There are no guarantees that they have told the truth.
Once a king was walking around a pool with his ministers（大臣）.Suddenly, he came up with（想出）an idea. He asked,“How many baskets of 41 are there in the pool?” The ministers couldn’t give an answer. The king was angry, “ You 42 answer my questions in three days!”Three days passed, but 43 of the ministers had the answer. Just then, a child said that he knew it. The king told the ministers 44 the child to the pool. To his surprise, the child 45 and said with a smile, “It is 46 . No need to go to the pool.” This made the king pleased. “All right. Let us know 47 .” The child said, “If you know the 48 of the basket, the answer is known. 49 it is as big as the pool, there is one basket of water; half as big, two baskets… ” “ Stop! That’s it .You have got the answer. They were thinking of things 50 a wrong way .”Sometimes to get out of the difficulty, one must change one’s way of thinking.41.________________A. fish B. flowers C. water
It’s disturbing to note how many of the crimes we do know about were detected ___not by systematic inspections or other security procedures.A. by accident B. on schedule C. in general D. at intervals
Moviegoers know that many special effects are created by computers．they often don′t know is that these scenes still require a lot of work．A.ThatB.WhomC.WhatD.How
How long have you worked here?（）ASince about two years.BI do not know.CFor about two years.DWho knows.
How long have you worked here?（）A、Since about two years.B、I do not know.C、For about two years.D、Who knows.
Do you know the girl over there?（）A、How can I know?B、Yes, I remember it now.C、It's Sam, my teacher's daughterD、She is a good girl.
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单选题‘‘May I know the question so that I can ______ for an answer?”Akbar said, “How many crows(乌鸦) are there in this city?”AaskBwaitCtryDreach
问答题Q2: Do you know any different customs of foreign countries? Can you show one or two examples?
问答题Almost all Americans want to be democratic, but many Americans are confused about what, exactly, democracy means. How do you know when someone is acting in a democratic or an undemocratic way? Recently several groups have spoken out with particular bitterness against the kind of democracy that means equal opportunity for all, regardless of race or national origin. They act as if all human beings did not belong to one species, as if some races of mankind were inferior to others in their capacity to learn what members of other races know and have invented. Other extremists attack religious groups—Jews or Catholics--or deny the right of an individual to be an agnostic. One reason that these extremists, who explicitly do not want to be democratic, can get a hearing even though their views run counter to the Constitution and our traditional values is that people who do want to be democratic are frequently muddled.
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问答题Let the children learn what all educated persons must some day learn, how to measure their own understanding, how to know what they know or do not know.