题目

设是两个非零向量，则“”是“”的（   ） A.充分不必要条件        B.必要不充分条件      C.充要条件              D.既不充分又不必要条件 答案：C依题意故等价于，故是充要条件.Imagine the situation. You are driving along a desert or on a mountain. You have no idea where you are. You passed the last house two hours ago. Then your car breaks down. It is night and it is cold. You have no mobilephone. What do you do? Well, next time take a GPS with you. Thisinvention may be able to help you. (61)It is a device(装置)which uses satellites__卫星) to find the user’s position(位置)__It can find your position to within 20 metres. A GPS cannot start your car, but at least you will know where you are.GPS, which means Global Positioning System, is a small radio receiver. It looks like a mobile phone. (62)You can hold it in your hand, or put in your pocket. It is sometimes put into a watch or a telephone. We also find GPS devices in cars, planes, or boats. Some of these devices have electronic (电子) maps, so you know where you are. For example, in a city they can tell you the name of the street.(63)_______.The first part is the receiver. You can hold it in your hand, or have it fixed into your car, plane, etc. The second part is a group of satellites orbiting the Earth. The receiver contacts at least four of the satellites and calculates(计算) its position. The third part of the system is a network of ground stations. They are all over the world. They control the satellites and make sure they are working well.(64)有些人认为未来GPS将会和手机一样普通 They are becoming cheaper and more and more accurate(精确的). There are also new uses for the GPS. Perhaps they will become like watches. Everyone will have one and you will never be lost again.【1】将此处划线的句子翻译成汉语。_________________________________________________【2】将此处改成被动语态句。______________________________________________________【3】请从如下选项中选出最能够使上下文语义连贯的一句。A. The Global Positioning System is so popular with users around the world.B. There are three parts to the Global Positioning System.C. The Global Positioning System is widely used in all kinds of fields(领域)D. Thanks to the Global Positioning System, we have improved our life a lot.【4】将此处划线的句子翻译成英语。_________________________________________________【5】请给本文给出恰当的标题。_____________________________________________________