题目

如图所示，相距为d的两平行金属板水平放置，开始开关S合上使平行板电容器带电.板间存在垂直纸面向里的匀强磁场.一个带电粒子恰能以水平速度v向右匀速通过两板间.在以下方法中，要使带电粒子仍能匀速通过两板（不考虑带电粒子所受重力）,正确的是（    ） A.把两板间距离减小一半，同时把粒子速率增加一倍B.把两板间距离增大一倍，同时把板间的磁场增大一倍C.把开关S断开，两板间距离增大一倍，同时把板间的磁场减小一半D.把开关S断开，Everyone needs friends. There is an old saying: Friends are God’s way of taking care of us. But how do you find real friendship and keep it?“The Care and Keeping of Friends” by American author Sally Seamans tells young students some smart ways to find friends.Sally says finding friendship is just like planting a tree. You plant the seed and take care of it to make it grow.First, you should choose a friend. What makes a good friend? It is not because a person has money or good looks. A good friend should be kind and patient. For example, if you have a bad day, a good friend should listen to your complaints(抱怨) and do their best to help. To make a friend, you cannot be too shy. You should make each other happy and share your lives.But things cannot always be happy. Even the best friends have fights. What should you do when you have a fight with your friend? You have to talk to them. When there is no one around, have an honest talk. If he or she doesn’t want to talk, you could write a letter.Sally says there are three steps to being friends again: Tell him or her how you are feeling; say what your friend has done wrong, and explain why you did this or that. The book also has advice on some small but important things like celebrating your friends’ success. Even if you haven’t had a real friend before, you will start to think of having one if you read this book. Because the book tells that friendship is the most important thing in your life.1.The writer of the text really wants to tell us________.A. life is great if we have friends B. an old saying C. Sally Seamans is an American writerD． God’s way of taking care of us2.“The Care and Keeping of Friends” is_______.A. the word of the GodB. a way of making good friends C. the name of a book by SallyD. a story from a newspaper3.A good friend should_______.A. have a lot of moneyB. have good looksC. be kind and patientD. listen to you4.Good friends will_______.A. always be happyB. do their best to help youC. never do wrongD. not have a fight5.What can’t you do if your good friend has done wrong?A. Write a letter to him or her.B. Have an honest talk with him or her.C. Tell him or her your feeling.D. Have a fight with him or her.