鉴别氮气和二氧化碳两种无色无气味的气体的最适宜的方法是（）

如图，△ABC中，AE交BC于点D，∠C=∠E，AD=4，BC=8，BD：DC=5：3，则DE的长等于(    )

Empathy

    Last year, researchers from the University of Michigan reported that empathy, the ability to understand other people, among college students had dropped sharply over the past 10 years.____Today, people spend more time alone and are less likely to join groups and clubs. Jennifer Freed, a co-director of a teen program, has another explanation. Turn on the TV, and you're showered with news and reality shows full of people fighting, competing, and generally treating one another with no respect.____There are good reasons not to follow those bad examples. Humans are socially related by nature.____Researchers have also found that empathetic teenagers are more likely to have high self-respect. Besides, empathy can be a cure for loneliness, sadness, anxiety, and fear.Empathy is also an indication of a good leader. In fact, Freed says, many top companies report that empathy is one of the most important things they look for in new managers.____ “Academics are important. But if you don't have emotional (情感的) intelligence, you won't be as successful in work or in your love life,” she says.What's the best way to up your EQ (情商）? For starters, let down your guard and really listen to others.____To really develop empathy, you'd better volunteer at a nursing home or a hospital, join a club or a team that has a diverse membership, have a “sharing circle” with your family, or spend time caring for pets at an animal shelter.

A. Everyone is different, and levels of empathy differ from person to person.

B. That could be because so many people have replaced face time with screen time, the researchers said.

C. “One doesn't develop empathy by having a lot of opinions and doing a lot of talking,” Freed says.

D. Humans learn by example—and most of the examples on it are anything but empathetic.

E. Empathy is a matter of learning how to understand someone else—both what they think and how they feel.

F. Good social skills—including empathy—are a kind of “emotional intelligence” that will help you succeed in many areas of life.

G. Having relationships with other people is an important part of being human—and having empathy is decisive to those relationships.

阅读理解

    One of the main challenges facing many countries is how to maintain their identity in the face of globalization and the growing multi-language trend. "One of the main reasons for economic failure in many African countries is the fact that, with a few important exceptions, mother-tongue education is not practiced in any of the independent African states." said Neville Alexander, Director of the Project for the Study of Alternative Education in South Africa at the University of Cape Town.

    In response to the spread of English and the increased multi-language trends arising from immigration, many countries have introduced language laws in the last decade. In some, the use of languages other than the national language is banned in public spaces such as advertising posters. One of the first such legal provisions(规定) was the 1994 "Toubon law" in France, and the idea has been copied in many countries since then. Such efforts to govern language use are often considered as futile by language experts, who are well aware of the difficulty in controlling fashions in speech and know from research that language switching among bilinguals is a natural process.

    It is especially difficult for native speakers of English to understand the desire to maintain the "purity" of a language by law. Since the time of Shakespeare, English has continually absorbed foreign words into its own language. English is one of the most mixed and rapidly changing languages in the world, but that has not been a barrier to acquiring superiority and power. Another reason for the failure of many native English speakers to understand the role of the state regulation is that it has never been the Anglo-Saxon way of doing things. English has never had a state-controlled authority for the language, similar, for example, to the Academic Francaise in France.

    The need to protect national languages is, for most western Europeans, a recent phenomenon—especially the need to ensure that English does not unnecessarily take over too many fields. Public communication, education and new ways of communication promoted by technology, may be key fields to defend.

如图，点A是⊙O上一动点，BC是⊙O的一条弦，且∠BAC=30°，点F、H分别是AB、AC的中点，直线FH与⊙O交于D、E两点．若DF+EH的最大值是12，则⊙O的半径是____