在图3所示的电路中，电源电压不变，闭合电键S，当滑动变阻器的滑片P向左移动时（    ）

它是促进北疆经济开发的生命线和联结统一多民族国家的纽带，它是指（    ）

Dear son,

    The day that you see me old and I am already not young, have patience and try to understand me.If I get dirty when eating, if I can not dress, have 1 Remember the hours I spent teaching it to you.

    If, when I 2 to you, I repeat the same things thousand and one times, do not interrupt me, listen to me.When you were small, I had to read to you thousand and one times the same story3 you get to sleep.

    When I do not want to have a shower, 4shame me nor scold me.Remember when I had to chase（追逐） you 5 thousand excuses I invented, in order that you wanted to bathe.

    When you see my ignorance on new technologies, give me the necessary time6 do not look at me with your mocking （嘲讽的） smile.I taught you how to do so many things: to eat well, to dress well, to confront（勇敢面对） life.

    When at some moment I 7the memory or the thread of our conversation, let me have the necessary time to remember.And if I cannot do it, do not become nervous, as the most important thing is not the8, but surely to be with you and to 9you listening to me.

    If 10, I do not want to eat, do not 11 me.I know well when I need to and when not.

    When my tired 12 do not allow me to walk, give me your hand---the same way13 I did when you gave your 14 steps.

    And when someday I say to you that I do not want to live any more, that I want to die, do not get angry.Some day you 15 understand.

    Try to understand that my age is not lived but survived.Some day you will discover that, 16 my mistakes, I always wanted the best thing for you and 17 I tried to prepare the way for you.

    You must not feel sad or angry for seeing me18 you.You must be next to me, try to understand me and to help me as I 19 it when you started living.

    Help me to walk; help me to 20 my way with love and patience.I will pay you by a smile and by the immense love I have had always for you.

    I love you, son.

Your father

阅读下面的文言文，完成文后各题。

   李牧者，赵之北边良将也。常居代①雁门，备匈奴，以便宜置吏，市租皆输入莫府②，为士卒费。日击数牛飨士，习射骑，谨烽火，多间谍，厚遇战士。为约曰：“匈奴即入盗，急入收保，有敢捕虏者斩！”匈奴每入，烽火谨，辄入收保，不敢战，如是数岁，亦不亡失，然匈奴以李牧为怯，虽赵边兵亦以为吾将怯。赵王让李牧，李牧如故。赵王怒，召之，使他人代将。

   岁余，匈奴每来，出战。出战，数不利，失亡多，边不得田畜。复请李牧。牧杜门不出，固称疾。赵王乃复强起使将兵。牧曰：“王必用臣，臣如前，乃敢奉令。”王许之。

   李牧至，如故约。匈奴数岁无所得，终以为怯。边士日得赏赐而不用，皆愿一战。于是乃选车得千三百乘，选骑得万三千匹，百金之士五万人，彀者十万人，悉勒***纵畜牧，人民满野。匈奴小入，详北不胜，以数千人委之。单于闻之，大率众来入，李牧多为奇阵，张左右翼击之，大破杀匈奴十余万骑。单于奔走。其后十余岁，匈奴不敢近赵边城。

   赵王迁七年，秦使王翦攻赵，秦多与赵王宠臣郭开金，为反间，言李牧欲反。赵王乃使赵葸及齐将颜聚代李牧。李牧不受命，赵使人微捕得李牧，斩之。后三月，王翦因急击赵，大破杀赵葸。虏赵王迁及其将颜聚，遂灭赵。

（节选自《史记·廉颇蔺相如列传》）

【注】①代：地名。②莫府：“莫”通“幕”；幕府，将帅在外的营帐，即为处理军政事务的衙署。