单选题Single mums are better at raising their kids than two parents—at least in the bird world. Mother zebra finches have to work harder and raise fewer chicks on their own, but they also produce more attractive sons who are more likely to get a mate. The finding shows that family conflict is as important an evolutionary driving force as ecological factors such as hunting and food supply. With two parents around, there's always a conflict of interests, which can have a detrimental effect on the quality of the offspring. In evolutionary terms, the best strategy for any parent in the animal world is to find someone else to care for their offspring, so they can concentrate on breeding again. So it's normal for parents to try to pass the buck to each other. But Ian Hartley from the University of Lancaster and his team wondered how families solve this conflict, and how the conflict itself affects the offspring. To find out, they measured how much effort zebra finch parents put into raising their babies. They compared single females with pairs, by monitoring the amount of food each parent collected, and removing or adding chicks so that each pair of birds was raising four chicks, and each single mum had two—supposedly the same amount of work. But single mums, they found, put in about 25 per cent more effort than females rearing with their mate. To avoid being exploited, mothers with a partner hold back from working too hard if the rather is being lazy, and it's the chicks that pay the price. "The offspring suffer some of the cost of this conflict," says Hartley. The cost does not show in any obvious decrease in size or weight, but in how attractive they arc to the opposite sex. When the chicks were mature, the researchers tested the "fitness" of the male offspring by offering females their choice of partner. Those males reared by single mums were chosen more often than those from two-parent families. Sexual conflict has long been thought to affect the quality of care given to offspring, says zoologist Rebecca Kilner at Cambridge University, who works on conflict of parents in birds. "But the experimental evidence is not great. The breakthrough here is showing it empirically." More surprising, says Kilner, is Hartley's statement that conflict may be a strong influence on the evolution of behaviour, clutch size and even appearance. "People have not really made that link," says Hartley. A female's reproductive strategy is usually thought to be affected by hunting and food supply. Kilner says conflict of parents should now be taken into account as well.

单选题What do you think this article is about? A. Learning a second language. B. Immigrants who become sick in the U. S.. C. Schools attended by immigrants to the U. S.. D. Language and its effect on the identity of immigrants.

单选题The widest benefits of the electronic revolution will accrue______the young.

单选题With the development of sophisticate instruments, earthquake will become predictable.

单选题Why is the program that's trying to save condors putting them into danger?

单选题How fit are your teeth? Are you lazy about brushing them? Never fear: An inventor is on the case. An electric toothbrush senses how long and how well you brush, and it lets you track your performance on your phone. The Kolibree toothbrush was exhibited at the International Consumer Electronics Show in Las Vegas this week. It senses how it is moved and can send the information to an Android phone or iPhone via a Bluetooth wireless connection. The toothbrush will be able to teach you to brush right (don't forget the insides of the teeth!) and make sure you're brushing long enough. "It's kind of like having a dentist actually watch your brushing on a day-to-day basis," says Thomas Serval, the French inventor. The toothbrush will also be able to talk to other applications on your phone, so developers could, for instance, create a game controlled by your toothbrush. You could score points for beating monsters among your teeth. "We try to make it smart but also fun," Serval says. Serval says he was inspired by his experience as a father. He would come home from work and ask his kids if they had brushed their teeth. They said "yes," but Serval would find their toothbrush heads dry. He decided he needed a brush that really told him how well his children brushed. The company says the Kolibree will go on sale this summer, for $ 99 to $ 199, depending on features. The U. S. is the first target market. Serval says that one day, it'll be possible to replace the brush on the handle with a brushing unit that also has a camera. The camera can even examine holes in your teeth while you brush.

单选题Soybean meat is similar to real meat ______.

单选题Britain is proud of her great poets; just as Italy is proud of her painters, and Germany ______of her composers.

单选题(According) to the graduate catalog, student housing (is) (more cheaper) (than) housing off campus.

单选题The word "Also" (line 2, para. 2) is used to ______.

单选题The influence of socialization process may

单选题His father has been working hard for many years to support him at university so he did not want to ______.

单选题He was ______ only by his wish to help me, and expected nothing in return.

单选题{{B}}Directions:{{/B}}Read the following text. Choose the best word(s) for each numbered blank and mark A, B, C or D on ANSWER SHEET 1. Most plants can make their own food from sunlight,{{U}} (1) {{/U}}some have discovered that stealing is an easier way to live, Thousands of plant species get by{{U}} (2) {{/U}}photosynthesizing, and over 400 of these species seem to live by pilfering sugars from an underground{{U}} (3) {{/U}}of fungi(真菌). But in{{U}} (4) {{/U}}a handful of these plants has this modus operandi been traced to a relatively obscure fungus. To find out how{{U}} (5) {{/U}}are{{U}} (6) {{/U}}, mycologist Martin Bidartondo of the University of California at Berkeley and his team looked in their roots. What they found were{{U}} (7) {{/U}}of a common type of fungus, so{{U}} (8) {{/U}}that it is found in nearly 70 percent of all plants. The presence of this common fungus in these plants not only{{U}} (9) {{/U}}at how they survive, says Bidartondo, but also suggests that many ordinary plants might prosper from a little looting, too. Plants have{{U}} (10) {{/U}}relations to get what they need to survive. Normal,{{U}} (11) {{/U}}plants can make their own carbohydrates through photosynthesis, but they still need minerals. Most plants have{{U}} (12) {{/U}}a symbiotic relationship with a{{U}} (13) {{/U}}network of what are called mycorrhizal fungi, which lies beneath the forest{{U}} (14) {{/U}}. The fungi help green plants absorb minerals through their roots, and{{U}} (15) {{/U}}, the plants normally{{U}} (16) {{/U}}the fungi with sugars, or carbon. With a number of plants sharing the same fungal web, it was perhaps{{U}} (17) {{/U}}that a few cheaters—dubbed epiparasites—would evolve to beat the system.{{U}} (18) {{/U}}, these plants reversed the flow of carbon,{{U}} (19) {{/U}}it into their roots from the fungi{{U}} (20) {{/U}}releasing it as "payment."

单选题{{B}}Passage Two{{/B}} A hundred years ago, the game we now call football did not exist. American football started during a game between two colleges. The teams had got together to play what they called "football", but each team played by different roles. One team played what we now call soccer. The other played what we now call rugby (橄榄球) . Both games had been invented a thousand years before. In the first kind of football game ever played, all the men from one village tried to kick a ball into another village. The men of the second village tried to kick the ball into the first. Hundreds of people joined in, running everywhere, running crops and knocking down fences. In time, people agreed on some rules to keep order, but many rules were left open to change. Different rules developed in different places. When the two colleges met to play football, each followed its own rules. They mixed the games together and invented a new game. A hundred years later we call that game American football. In what ways do you suppose the game we know now will have changed in another hundred years?