单选题 求与两球面,均相切的圆柱面方程. A、 B、 C、 D、

单选题设向量组(Ⅰ)是向量组(Ⅱ)的线性无关的部分向量组，则

单选题A=[234]，r(A+AB)=2，则t=()．(A)10(B)9(C)8(D)7

单选题=______。A．B．C．D．

单选题5个人从左到右排成一排，其中甲不在中间，乙不在末尾，不同的排法有______

单选题设x∈R，记不超过E的最大整数为[x]，令{x}=x-[x]，则______

单选题下列命题①设函数f(x)在(a，b)内可导，且f(a)=f(b)，则至少有一点ξ∈(a，b)，使f'(ξ)=0②设函数f(x)在[a，b]上连续，在(a，b)内可导，且有一点ξ∈(a，b)，使f'(ξ)=O，则必存在x1，ξ∈(a，b)，使得f(x1)=f-(x2)③设函数f(x)在(a，b)内可导，，则至少有一点ξ∈(a，b)，使f'(ξ)=0④设函数f(x)在[a，+∞)上连续，在(a，+∞)内可导，且，则至少有一点ξ∈(a，+∞)，使f'(ξ)=0中正确的是(A)①、③．(B)①、④．(C)②、③．(D)③、④．

单选题4个车间合作生产一批服装，其中甲车间生产了92件，乙车间生产的是另外3个车间生产数量之和的，丙车间生产的是另外3个车间生产数量之和的，丁车间生产的是另外3个车间生产数量之和的，则这批服装共有()件．(A)180(B)192(C)216(D)228(E)240

单选题 Passage 4 In her 26 years of teaching English, Shannon McGuire has seen countless misplaced commas, misspelled words and sentence fragments. But the instructor at US's Louisiana State University in Baton Rouge said her job is getting harder every day. "I kid you not, the number of errors that I've seen in the past few years have multiplied five times," she said. Experts say email and instant messaging are at least partly to blame for an increasing indifference toward the rules of grammar, spelling and sentence structure. They say the problem is most noticeable in college students and recently graduates. "They used to at least feel guilty (about mistakes)," said Naomi Baron, professor of linguistics at American University in Washington, D. C. "They didn't necessarily write a little better, but at least they felt guilty." Ironically, Baron's latest book, "Alphabet to Email: How Written English Evolved and Where It's Heading," became a victim of sloppy proofreading. The book's title is capitalized differently on the cover, spine and title page. "People used to lose their jobs over this," she said. "And now they just say 'whatever'." "Whatever" describes Jeanette Henderson's attitude toward writing. The sophomore at the University of Louisiana at Monroe admits that her reliance on spellcheck has hurt her grades in English class. "Computer has spoiled us," she said. But the family and consumer sciences major believes her future bosses won't mind the mistakes as much as her professor does. "They're not going to check semicolons, commas and stuff like that," Henderson said. LSU's McGuire said she teaches her students to use distinct writing styles that fit their purpose. She emphasizes that there's the informal language of an email to a friend, but there's also the well thought out and structured academic or professional style of writing. It's not just email and instant messaging that are contributing to slack writing habits. Society as a whole is becoming more informal. Casual wear at work used to be reserved for Friday, for example, but is now commonplace at most offices. There's also a greater emphasis on youth culture, and youth tend to use instant messaging more than adults do. English language has been neglected at different points in history but always rebounds. During Shakespearen times, for example, spelling wasn't considered important, and early publishers rarely proofread. There will likely be a social force that recognizes the need for clear writing and swings the pendulum back.

单选题下列函数中在点x=0处可导的共有A．1个.B．2个.C．3个.D．4个.

单选题____