题目

已知为纯虚数，且为虚数单位），则（    ） A．1    B．    C．    D．    答案：D 【解析】设，则，即，所以，则，故选D． 短文改错 假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处错误，每句中最多有两处。错误涉及一个单词的增加、删除或修改。 增加：在缺词处加一个漏词符号(∧)，并在此符号下面写出该加的词。 删除：把多余的词用斜线(＼)划掉。 修改：在错的词下划一横线，并在该词下面写出修改后的词。 注意：1．每处错误及其修改均仅限一词； 2．只允许修改10处，多者(从第11处起)不计分。 　　It is a long time since you come to Beijing to learn Chinese．How are you getting along well with your study? I' m eager to know whether you are used to live in Beijing or not．There is go-ing to have an English speech contest in Beijing in July．It' s such important for me that I want to do it well．Therefore, I have some trouble in collecting information I need．That also puzzles me is how to put what I have learned into practice．I know you have good command of English． 　　Would you please make me a favor? I' d appreciate this if you can give me some advice on how to solve these problems．After the speech contest,I will call on you．