题目

关于电磁波，下列说法不正确的是（  ）A．不同波长的电磁波在真空中传播速度不同B．电磁波可以在真空中传播，声波不可以在真空中传播C．光实际上也是一种电磁波，可以用来传递信息和能量D．微波、无线电波、红外线、紫外线都属于电磁波，超声波不是电磁波 答案：A 【解析】 试题分析：光波属于电磁波，所有电磁波的速度都等于光速，并且电磁波的波长与频率互成正比例关系．电磁波可以传递信息和能量． 声音的传播需要介质，声音不能在真空中传播． 【解析】 A、所有电磁波在真空中的传播速度都是相同的，等于光速，故A错误； B、电磁波可以在真空中传播The “Doorman”On a trip to California, my family stopped for lunch. As we walked toward the entrance to the restaurant, a man, with a   36  beard and dirty hair, jumped up from a bench and opened the door for us．Regardless of his   37 , he greeted us in a friendly way． Once inside, my daughters whispered, "Mom, he   38   " After we ordered our lunch, I explained, telling the kids to look   39  the dirt．We then watched other customers approach the restaurant but many   40  him．Seeing this rudeness truly upset me．The day I became a mother, I had decided to set a good   41  for my children．Yet sometimes when things didn't go right, being a good example was   42   When our meal arrived, I realized I had left the car-sick pills in the truck．With the windiest trip ahead, the kids needed them, so I   43  myself from the meal and went to get them．Just then, the "doorman" was opening the door for a couple．They rushed past him without even acknowledging his   44   . Letting them in first, I said a loud "thank you" to him as I 45 ．When I returned, we talked a bit．He said he was not allowed inside   46  he purchased food．I went back and told my family his   47 . Then I asked our waitress to add one soup and sandwich．The kids looked   48  as we had already eaten, but when I said the order was for the "doorman" , they smiled．When it was time to   49  our trip, I noticed the "doorman" enjoying his meal．Upon seeing me, he stood up and thanked me heartily．He then   50  his hand for a handshake and I gratefully accepted．I suddenly noticed the tears in his eyes—tears of  51  .  What happened next drew great astonishment: I gave the " doorman" a   52  ! He pulled away, with tears   53  down his face．Back in truck, I fell into deep thought．While we can't choose many things in life, we can choose when to show gratitude．I said thanks to a man who had   54  held open a door for me, and also said thanks for that   55  to teach my children by example．小题1:A．heavyB．messyC． long D． grey小题2:A．serviceB．statusC． appearance appearanceD． attitude小题3:A．smellsB．smilesC． sniffsD． smokes小题4:A．intoB．overC． aroundD． beyond小题5:A．hatedB．missedC． ignoredD． refused小题6:A．exampleB．ruleC． recordD． target小题7:A．toughB．accessibleC． awkwardD． stressful小题8:A．withdrewB．freedC． preventedD． excused小题9:A．companyB．effortC． presenceD． attempt小题10:A． quittedB．exitedC． marchedD． approached小题11:A． beforeB．thoughC． unlessD． since小题12:A． demandB．deedC． experienceD． story小题13:A． concernedB．puzzledC． shockedD． bored小题14:A． continueB．startC． takeD． make小题15:A． wavedB．washedC． raisedD． extended小题16:A． gratitudeB．affectionC． sympathyD． approval小题17:A． nodB．hugC．liftD． clap小题18:A． streamingB．slippingC． rushingD． breaking小题19:A． firmlyB．simplyC． constantlyD． politely小题20:A． journeyB．wisdomC． coincidenceD． opportunity