题目

下列命题中： ①若2弧度的圆心角所对的扇形的弦长为2，则扇形的弧长为； ②若k＜－4，则函数y＝cos2x＋k(cosx－1)的最小值是1； ③若，O为坐标原点，则在方向上的投影是； ④在平行四边形ABCD中，E、F分别是AB、BC边中点，设，则 其中命题正确的序号是_______________。 答案：①②④阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。BNonverbal （非语言的）CommunicationWhen you are in another country, it is important to know the language, but it is equally important to know how to communicate nonverbally. Before saying anything, people communicate nonverbally by making gestures. According to an investigation(调查),only 30 to 35 percent of our communication is verbal. When people don't know the language, the most common way to communicate is through gestures. However, many gestures have different meanings, or no meaning at all, in different parts of the world.In the United States, for example, nodding your head up and down means “yes”. In some parts of Greece and Turkey, however, this motion can mean “no”. In Southeast Asia, nodding your head is a polite way of saying “I've heard you.”In ancient Rome, when the emperor wanted to spare someone's life, he would put his thumb up. Today in the United States, when someone puts his/her thumb up, it means “Everything is all right.” However, in Sardinia and Greece, the gesture is insulting (侮辱)and should not be used there.In the United States, raising your clasped(握紧的) hands above your head means “I'm the champion” or “I'm the winner”. It is the sign that prizefighters make when they win a fight. When a leading Russian statesman(政治家) made this gesture after a White House meeting, Americans misunderstood and thought he meant he was a winner. In Russia, however, it is a sign of friendship.There are other nonverbal signals that people should be aware of when they go to another country, such as the distance to maintain between speakers. Americans stand closer to each other than English people. English people don't like touching somebody or being touched. Now in America, touch is important. For example friends touch each other on the arm. They often put an arm around a friend when they say “hello” or “goodbye”.（1）It is very important to know how to communicate nonverbally when you are in another country because .A.most people speak different languagesB.much of our communication is nonverbal on many occasionsC.people usually make gestures before saying anythingD.it's easy to learn how to express oneself through gestures（2）If a native in Singapore nods his head up and down when you talk to him, his motion means .A.yesB.noC.that's all rightD.I've heard you（3）When the Russian leader put up his clasped hands after the meeting at the White House .A.he meant Russia was the winnerB.he was insulting AmericaC.he made a show of friendship to AmericaD.he in fact meant nothing at all（4）The gesture of putting one's thumb up should not be used when you are travelling in .A.ChinaB.the United StatesC.GreeceD.Southeast Asia