题目

已知向量，且，则的值为（ ）A. 1 B. 3 C. 1或3 D. 4 答案：【答案】B【解析】先求出，再利用向量垂直的坐标表示得到关于的方程，从而求出. 因为，所以，因为，则，解得所以答案选B.按照提示完成下列句子。（注意使用正确的形式，每小题1分。）1.Gaudi the project from 1882 until his death in 1926.(从事)2. size and population, how big is the Europe Union compared with China? (根据……/ 依照……)3. , the number increased during the second half of the twentieth century. (逐渐地)4.The bottom ten countries are all African countries, with Sierra Leone (in West Africa) the list.(在……底部)5.The second important goal is to that all children have education up to the age of 11. (确保)6. , there are 800 tornadoes in the US each year, causing about 80 deaths and 1,500 injuries. (平均来说) 7.Tornadoes can the fur the back of a cat and the feathers off a chicken. (去掉)8.The cemetery where Coghlan was buried was destroyed by the hurricane and Coghlan’s coffin in the sea. (结束，告终) 9.Hundreds of houses when the lava reached them. (着火)10.During the Renaissance, some of the greatest painters lived and worked in Florence. (有史以来)