Many signals that animals makeseemtoimposeonthe signalers costs that are overly damaging. Aclassicexample is noisy begging bynestlingsongbirds when a parent returns to thenestwith food. These loud cheeps and peeps might give the location of thenestaway to a listeninghawkor raccoon, resulting in the death of thedefenselessnestlings. In fact, when tapes of begging tree swallows were played at anartificialswallownestcontaining an egg, the egg in that “noisy”nestwas taken or destroyed by predators before the egg in a nearby quietnestin 29 of 37 trials.

Furtherevidencefor the costs of begging comes from a study of differences in the begging calls of warblerspeciesthatneston the groundversusthose thatnestin therelativesafety of trees. The young of ground-nesting warblers produce begging cheeps of higher frequencies than do their tree-nesting relatives. These higher-frequency sounds do not travel as far, and so may betterconcealthe individuals producing them, who are especiallyvulnerableto predators in their ground nests. David Haskell createdartificialnests withclayeggs and placed them on the ground beside a tape recorder that played the begging calls of either tree-nesting or of ground-nesting warblers. The eggs “advertised” by the tree-nesters' begging calls were found bittensignificantlymore often than the eggs associated with the ground-nesters' calls.

Thehypothesisthat begging calls have evolved properties that reduce theirpotentialfor attracting predators yields a prediction: baby birds ofspeciesthat experience high rates ofnestpredationshould produce softer begging signals of higherfrequencythan nestlings of otherspeciesless often victimized bynestpredators. This prediction was supported bydatacollected in onesurveyof 24speciesfrom an Arizona forest, moreevidencethatpredatorpressurefavors theevolutionof begging calls that are hard todetectandpinpoint.

Giventhat predators can make it costly to beg for food, whatbenefitdo begging nestlingsderivefrom their communications? One possibility is that a noisy baby bird providesaccuratesignals of its real hunger and good health, making itworthwhilefor the listening parent to give it food in anestwhere several otheroffspringare usuallyavailableto be fed. If thishypothesisis true, then it follows that nestlings shouldadjustthe intensity of their signals in relation to the signals produced by their nestmates, who arecompetingfor parentalattention. When experimentally deprived baby robins are placed in anestwithnormallyfed siblings, the hungry nestlings beg more loudly than usual—but so do their better-fed siblings, though not as loudly as the hungrier birds.

If parent birds use begging intensity to direct food to healthyoffspringcapableofvigorousbegging, then parents should make food delivery decisions on the basis of their offsprings’ calls. Indeed, if you take baby tree swallows out of anestfor an hour feeding half the set and starving the other half, when the birds are replaced in thenest, the starved youngsters beg more loudly than the fed birds, and the parent birds feed the active beggars more than those who beg less vigorously.

As these experiments show, begging apparently provides asignalof need that parents use to make judgments about whichoffspringcanbenefitmost from a feeding. But the question arises, why don't nestlings beg loudly when they aren't all that hungry? By doing so, they could possiblysecuremore food, which should result in more rapid growth or larger size, either of which isadvantageous. The answer lies apparently not in the increased energy costs of exaggerated begging—such energy costs are smallrelativeto thepotentialgain in calories—but rather in the damage that any successful cheater would do to its siblings, which share genes with one another. An individual's success in propagating his or her genes can be affected by more than just his or her ownpersonalreproductivesuccess. Because close relatives have many of the same genes, animals that harm their close relatives may in effect be destroying some of their own genes. Therefore, a beggingnestlingthat secures food at the expense of its siblings might actually leave behind fewer copies of its genesoverallthan it mightotherwise.

Questions:
question_stem: The phrase “impose on” in the passage is closest in meaning to
choices: tag: A
text: increase for

tag: B
text: remove from

tag: C
text: place on

tag: D
text: distribute to
answer_key: C
explanation: C impose on: 施加影响于，强迫。A 是为…增加；B 是从…移除；C 是在…上施加；D 是分配给。所以答案 place on 施加是正确答案。 对应原文 Many signals that animals make seem to impose on the signalers costs that are overly damaging. 首先看 impose 本身，im 表示在什么什么之内，pose 表示放置，所以凑起来是放在什么什么里面，能猜出放的意思，所以 place 靠谱。原句说动物发出的信号会怎么样发信号那个动物，A 增加 B 挪走 D 分给那个动物都完全不对。

question_stem: According to paragraph 1, the experiment with tapes of begging tree swallows establishes which of the following?
choices: tag: A
text: Begging by nestling birds can attract the attention of predators to the nest.

tag: B
text: Nest predators attack nests that contain nestlings more frequently than they attack nests that contain only eggs.

tag: C
text: Tapes of begging nestlings attract predators to the nest less frequently than real begging calls do.

tag: D
text: Nest predators have no other means of locating bird nests except the begging calls of nestling birds.
answer_key: A
explanation: A 以 tapes of begging tree swallows 做关键词定位至最后一句，但这就话只说明放了 tape 的 nest 会遭受更多攻击，没说为什么，往前看，上句说 cheeps 泄露了信息给捕食者，使得鸟窝遭受攻击，然后就举了 tape 的例子，无非是说 cheeps 吸引了攻击，所以 A 正确。B 和 C 的两个比较原文没说，D 的没有其他手段也没说。

question_stem: The word “artificial” in the passage is closest in meaning to
choices: tag: A
text: attractive

tag: B
text: not real

tag: C
text: short-term

tag: D
text: well designed
answer_key: B
explanation: well designed" "artificial: 人造的，人工的，虚假的。A 是吸引人的；B 是不真实的；C 是短期的；D 是良好设计的。所以答案 not real 正确。 对应原文 David Haskell created artificial nests with clay eggs and placed them on the ground beside a tape recorder that played the begging calls of either tree-nesting or of ground-nesting warblers. 原文说这个人做了一个什么样的 nest，之前的句子说幼鸟在 ground nest 很容易受攻击，紧接着就说做了一个 nest，后半句话说了旁边放了一个录音播放叫声，所以肯定是假的，ACD 都不沾边。

question_stem: Paragraph 2 indicates that the begging calls of tree nesting warblers
choices: tag: A
text: put them at more risk than ground-nesting warblers experience

tag: B
text: can be heard from a greater distance than those of ground-nesting warblers

tag: C
text: are more likely to conceal the signaler than those of ground-nesting warblers

tag: D
text: have higher frequencies than those of ground-nesting warblers
answer_key: B
explanation: B 此题较难，需要阅读较多内容，因为关键词 tree-nestling warblers 多次出现。后半段说了 David 的实验，所以只是一个事实，往前看，看到第二句和第三句说 ground-nestling 的鸟发出的声音是高频的，传播的不远，而 tree-nestling 与之相反，所以答案 B 传播的更远正确。C 和 D 明显说反；B 和 C 是意思相反的答案。A 具有迷惑性，原文只是说在试验中 tree nestling 的鸟蛋被咬得很惨，没说 tree 的就一定比 ground 的危险。

question_stem: The experiment described in paragraph 2 supports which of the following conclusions?
choices: tag: A
text: Predators are unable to distinguish between the begging cheeps of ground-nesting and those of tree-nesting warblers except by the differing frequencies of the calls.

tag: B
text: When they can find them, predators prefer the eggs of tree-nesting warblers to those of ground-nesting warblers.

tag: C
text: The higher frequencies of the begging cheeps of ground-nesting warblers are an adaptation to the threat that ground-nesting birds face from predators.

tag: D
text: The danger of begging depends more on the frequency of the begging cheep than on how loud it is.
answer_key: C
explanation: C 排除法，A 选项原文完全没有对应，原文没说除了 frequency 什么方法都没有；B 原文也没有对应，没说 predator 更喜欢哪个；C 选项正确，对应原文第二句和第三句；D 选项没有对应。

question_stem: The word “prediction” in the passage is closest in meaning to
choices: tag: A
text: surprise

tag: B
text: discovery

tag: C
text: explanation

tag: D
text: expectation
answer_key: D
explanation: D predict: 预测，预期，预报。A 是惊讶；B 是发现；C 是解释；D 是预期。所以 D 的 expectation 正确。pre 在什么什么之前，dict 说，凑起来就是预测。   对应原文 The hypothesis that begging calls have evolved properties that reduce their potential for attracting predators yields a prediction: ...   原文说 hypothesis(假设)产生了一个什么，冒号后是解释，假设产生的东西肯定不是已经实现的，discovery 和 explanation 都不对，surprise 更多地表现主观情绪，不选。

question_stem: The word “pinpoint” in the passage is closest in meaning to
choices: tag: A
text: observe

tag: B
text: locate exactly

tag: C
text: copy accurately

tag: D
text: recognize
answer_key: B
explanation: B pinpoint: 精确找到，瞄准。A 是观察；B 是精准定位；C 是准确的复制；D 是认知。所以 B 的 locate exactly 正确。pin 大头针，point 点，用大头针点当然很精确。

question_stem: The word “derive” in the passage is closest in meaning to
choices: tag: A
text: require

tag: B
text: gain

tag: C
text: use

tag: D
text: produce
answer_key: B
explanation: B derive: 获取，获得。A 是要求；B 是获得；C 是使用；D 是制造。所以 B 的 gain 正确。 对应原文 Given that predators can make it costly to beg for food, what benefit do begging nestlings derive from their communications? 原句说：既然 begging 很危险，鸟能从 begging 中 derive 什么好处？后面马上给出回答，说一是 noisy bird 有食物吃，二是 blabla，也就是鸟能从 begging 当中得到的东西，所以 derive 得到，要求使用和产生都不对。

question_stem: In paragraphs 4 and 5, what evidence supports the claim that the intensity of nestling begging calls is a good indicator of which offspring in a nest would most benefit from a feeding?
choices: tag: A
text: When placed in a nest with hungry robins, well-fed robins did not beg for food.

tag: B
text: Among robin nestlings, the intensity of begging decreased the more the nestlings were fed.

tag: C
text: Hungry tree swallow nestlings begged louder than well-fed nestlings in the same nest.

tag: D
text: Hungry tree swallow nestlings continued to beg loudly until they were fed whereas well-fed nestlings soon stopped begging.
answer_key: C
explanation: C 排除法。A 的 robins 做关键词定位至第四段最后一句，原文说即使 well-fed 的鸟也叫，只是叫的不厉害罢了，所以 C 正确，A 说反；同一句话可以得到 B 没说，原文没说喂食越多鸟越不叫；D 的 whereas 之前是对的，但原文也没说 well-fed 的很快就不叫了，应该是继续叫。

question_stem: It can be inferred from paragraphs 4 and 5 that parent songbirds normally do not feed
choices: tag: A
text: nestlings that are too weak to beg for food as vigorously as their nestmates

tag: B
text: more than one hungry nestling during a single visit to the nest

tag: C
text: offspring that were fed by the parents on the previous visit to the nest

tag: D
text: nestlings that have been removed and then later put back into their nest
answer_key: A
explanation: A 承接上一题，从上一题就可以知道，叫的越激烈，越容易得到喂食，所以就可以退出如果叫的太弱的话，就得不到喂食，对应 A 选项。

question_stem: In paragraph 6, the author compares the energy costs of vigorous begging with the potential gain in calories from such begging in order to
choices: tag: A
text: explain why begging for food vigorously can lead to faster growth and increased size

tag: B
text: explain how begging vigorously can increase an individual’s chance of propagating its own genes

tag: C
text: point out a weakness in a possible explanation for why nestlings do not always beg vigorously

tag: D
text: argue that the benefits of vigorous begging outweigh any possible disadvantages
answer_key: C
explanation: C 首先根据问题中的比较定位至第四句，说 such energy costs are small relative to the potential gain in calories，先把所在的句子读清楚，说这种夸张的 begging 会对其他的 sibling 造成伤害，进而伤害到整个群体，所以答案是 C，给出一个鸟夸张 begging 的缺点。A 说了但不是目的；B 没说 D 说反。

question_stem: According to paragraph 6, which of the following explains the fact that a well-fed nestling does not beg loudly for more food?
choices: tag: A
text: There is no benefit for a nestling to get more food than it needs to survive.

tag: B
text: By begging loudly for food it does not need, a nestling would unnecessarily expose itself to danger from predators.

tag: C
text: If a nestling begs loudly when it is not truly hungry, then when it is truly hungry its own begging may be drowned out by that of its well-fed siblings.

tag: D
text: More of a nestling's genes will be passed to the next generation if its hungry siblings get enough food to survive.
answer_key: D
explanation: D，从上一题的第四句读起，说会伤害 sibling，紧接着说同一物种有很多共同基因，伤害 siblings 意味着伤害整个物种的基因，所以 D 正确。其他都没说。