题目

将地面上静止的货物竖直向上吊起，货物由地面运动至最高点的过程中，v﹣t图象如图所示．以下判断正确的是（） A . 前2s内与最后2s内货物的平均速度和加速度都相同 B . 前2s内货物处于超重状态 C . 最后2s内货物只受重力作用 D . 第2s末至第6s末的过程中，货物的机械能守恒 答案：B If you go into the forest with friends, stay with them. If you don’t, you may get lost. If you get lost, this is what you should do. Sit down and stay where you are. Don’t try to find your friends—let them find you. You can help them find you by staying in one place. There is another way to help your friends or other people to find you. You can shout or whistle three times. Stop. Then shout or whistle three times again. Any signal given three times is a call for help.     Keep up shouting or whistling. Always three times together. When people hear you, they will know that you are not just making a noise for fun. They will let you know that they have heard your signal. They will give you two shouts or two whistles. When a signal is given twice, it is an answer to a call for help.     If you don’t think that you will get help before night comes, try to make a little house with branches. Make yourself a bed with leaves and grass.     When you need some water, you have to leave your little branch house to look for it. Don’t just walk away. Pick off small branches and drop them as you walk in order to go back again easily. When you are lost, the most important thing to do is to stay in one place. 63. Which signal is a call for help?    A. shouting here and there  B. crying twice    C. shouting or whistling three times together  D. whistling every where in the forest 64. When you hear two shouts or two whistles, you know that ______.    A. someone is afraid of an animal                 B. people will come to help you    C. someone needs help              D. something terrible will happen 65. What’s the meaning of the underlined sentence?    A. Leave branches to find your way back   B. Pick off branches to build another house C. Use branches to make a bed                              D. Drop branches to look for water 66. The main idea of the passage is______. A. how to travel in the forest                            B. how to spend the night in the forest C. what you should do if you want to get some water D. what you should do if you are lost in the forest