单选题设，则下列结论中错误的是()．

单选题设，若，则n的最小值为()。A．7B．8C．9D．10

单选题已知函数f(x)在x=a处可导，则=______。A．f'(a)B．2f'(a)C．0D．f'(2a)

单选题设A，B，C，D是扎阶矩阵，A可逆H=，则|H|={{U}}{{/U}}．A.|A||B-DA-1C|B.|A||B|C.|A||B|-|C||D|D.-|C||D|

单选题直线ax-by=0与圆x2+y2-ax+by=0(a,b≠0)的位置关系是( )。

单选题设an=-n2+10n+11，则数列an从首项到第几项的和最大( )． (A) 10 (B) 11 (C) 10或11 (D) 12

单选题函数f(x)=ax(a＞0，且a≠1)，对于任意的实数x，y，都有______。 A．f(xy)=f(x)·f(y) B．f(xy)=f(x)+f(y) C．f(x+y)=f(x)·f(y) D．f(x+y)=f(x)+f(y)

单选题{{B}}Directions:{{/B}}There are 5 reading passages in this part. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C, and D. You should decide on the best choice and mark your answer on the ANSWER SHEET by blackening the corresponding letter in the brackets. For years, doctors have given cancer patients three main treatments: surgery, radiation and chemotherapy. Now researchers are developing a fourth weapon: the patient's own immune system. New vaccines and drugs can stimulate the production of an army of cells and antibodies that kill cancer cells. Drug-vaccine therapy may lie lifesaver for Deerfield man. Few people survive advanced melanoma, but immune therapy is giving Deerfield resident Douglas Parker a fighting chance. The 46-year-old salesman noticed a mole on his chest three and a half years ago that was found to be cancerous. Doctors removed the mole but didn't get all of the cancer. The cancer spread to other parts of his body, including his liver, where a tumor grew as large as a baseball. Parker took interferon and interleukin-2 to boost his immune system's ability to fight the cancer. The tumor shrank but didn't disappear. In August, 1997, surgeons removed it, along with two thirds of his liver. Last January, doctors discovered a new tumor on Parker's left adrenal gland. He received an experimental cancer vaccine at the University of Chicago Hospitals, but the vaccine didn't stop the cancer from spreading to his right adrenal gland. To augment the vaccine, doctors at Lutheran General Hospital gave Parker a new round of intcrleukin-2 and interferon. The drug-vaccine combination has shrunk the tumors. And while it's too early to pronounce Parker cured, immune therapy may save his life. "I want to do this to help myself as well as other people who have melanoma," he said. Immune therapy "ultimately will be a significant change in the way we treat a lot of different cancers," said Dr. Jon Richards of Lutheran General Hospital in Park Ridge, who is testing cancer vaccines on melanoma patients. "It will be an equal partner with the other three treatments in the next five to ten years." Several drugs that bolster the immune system have been approved, and vaccines are being tested in dozens of clinical trials, including several in the Chicago area. Many of the experimental vaccines have been tested on patients with advanced melanoma who have little chance of surviving with conventional treatments alone. Researchers also have begun doing work that could lead to vaccines to treat prostate, lung, colon and other cancers. Immune therapy alone won't cure cancer. But when used after conventional treatments, it could kill cancer cells that survive surgery, radiation or chemotherapy, researchers said. Some day, vaccines also might be able to prevent certain cancers. It may be possible to vaccinate against viruses and bacteria that help cause cervical, liver and stomach cancers, the National Cancer Institute said.

单选题装台机器需要甲，乙，丙三种部件各一件，现库中存有这三种部件共270件，分别用甲，乙，丙库存件数的装配若干机器，那么原来存有甲种部件()．

单选题关于x的方程的根的个数为()．

单选题已知a1=2，a2=2，且an=|an-1-an-2|，n=3,4,5,…，则a20，a21和a22的值分别是( )．

单选题不等式ax2+bx+2＞0的解集为，则2x2+bx+a＞0的解集为______

单选题A，B，C，D，E五个队参加排球循环赛，每两队只赛一场，胜者得2分，负者得0分，比赛结果是：A，B并列第一；C第三；D，E并列第四，则C队得分为______

单选题设4×3矩阵A的秩r(A)=2，B=，则r(AB)=()．

单选题．