题目

设向量a，b，c满足a+b+c=0，且a⊥b,|a|=1,|b|=2,则|c|2的值为(    )A.1                  B.2                  C.4                  D.5 答案：解析:∵a⊥b,∴a·b=0.由a+b+c=0知,c=-(a+b).∴|c|2=a2+2a·b+|b|2=5,选D.答案:D Rob Frenette had problems with bullies (欺辱) at school for eleven years. He was often lonely and scared. When he was fifteen, however, he decided to do something about his problems. He walked into a newspaper office and told them about the bullying. His story went into the newspaper and soon all the TV stations in Canada wanted to talk to him about his experiences. They also wanted to hear his ideas to stop bullying.After that, Rob continued his studies at school, but in his free time he helped other people with bullying problems. With a friend Katie Neu, he made a website called www. bullyingcanada. ca. Visitors to the website can find advice, stories and poems about bullying, in both English and French. When people are upset, they can talk on the phone or online to Rob and his team. Every weekend Rob has to answer e-mails to the website. He also speaks to children, teachers and members of government around the country about bullying.Rob’s most important message is: “When bullies are unkind to you, it isn’t your fault. There’s nothing wrong with you, so you should try to keep trusting yourself. And remember that people care about your problems. You just have to find those people.”One of Rob’s ideas is “Blue Day”, a special day for stopping bullying in schools. Students have to wear blue clothes and in class they learn how to stop bullying. More than 150 Canadian schools now celebrate Blue Day, but Rob won’t stop until there’s a Blue Day in every school in Canada.1.How did Rob often feel at school before he was fifteen?A.Relaxed. B.Unhappy. C.Excited. D.Tired.2.We can learn from this passage that Rob suffered from bullying since he was .A.four B.seven C.eleven D.fifteen3.www. bullyingcanada. ca is a website where people can .A.learn how to write poems B.get blue clothes for freeC.get advice about bullying problems D.practice both English and French4.What was the correct order in which these events happened?a. Rob and his friend made a website. b. Rob was bullied at school.c. Rob created “Blue Day”. d. Rob told his story in public.A.c-b-a-d B.a-b-c-d C.b-a-d-c D.b-d-a-c