题目：
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| "So teach him to close the door", my daughter Emma responded after listening to me 1 , again, about the dog coming in from the back door, bringing with him a blast of Buffalo January 2 air. Teach a dog to close a door behind him? That has got to be a really, really 3 thing to do.But then she took it a step 4 . "Come on Kolby", she said, grabbing (抓住) some treats and 5 him in front of the open door. "Touch." And "touch" he did, which moved the door to a 6 position. She 7 him with a treat, smiled, looked at me, and said "see!" And I saw and became 8 . Over the last few days I have been consistent (一致的) with Kolby. Each time he comes in I 9 him back to the open door patiently and ask him to close.There have been 10 in the beginning, but lately more and more successes. However, there remains much work to be done.I have to get him follow my hand signal again and again 11 he will close the door from a distance. But, I now realize, as long as you keep to the 12 , the task will be completed, and, with the way things are progressing, 13 quickly. What a 14 treat to have a dog that can close the door after himself! Even more wonder can be found in the 15 I learned so clearly from both Emma and Kolby. A wish is just a wish until you decide to take 16 . Once you 17 the belief that it is"too hard", then it remains "too hard" and out of 18 . Once you decide to accomplish a goal, and 19 that it is"easy", then it becomes "easy" to do what needs to be done. Just 20 doing it. | ||||
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①因铁在氯气中燃烧生产氯化铁，发生化合反应，故①正确；②因三氧化硫与水化合生成硫酸，发生化合反应，故②正确；③因氨气和氯化氢反应生成氯化铵，发生化合反应，故③正确；④因氮气和氧气在放电条件下生成一...
