下图是某生物兴趣小组同学在探究“口腔内的化学性消化”时的实验过程，请你分析该过程。
（1）1号试管所起的作用是与2号试管进行 。
（2）在步骤D加碘液2滴后颜色不变蓝的是______，其原因是_____________________。
（3）如果将C过程烧杯中的水换为5℃，再重复D过程，发现滴加碘液后两支试管中都变为蓝色，这说明唾液中的淀粉酶要发挥作用必须在_____________。
（1）对照
（2）2；唾液中的淀粉酶将淀粉消化分解
（3）适宜的温度
完形填空（共20题，每小题1.5分，满分30分） 阅读下面短文，掌握其大意，然后从36—55各题所给的四个选项（A、B、C和D）中，选出最佳选项，并将答案填入答题卡中。 When I was younger, I belonged to a club that did community service work. There was one specific event that was 36 for me. We spent four hours handing out warm dinner to the homeless in the streets. After that we went to a(n) 37 shelter. I was in high school at the time and my sister was too 38 to take part. She wanted to 39 , so she made sixty cookies for us to take and 40 to people. When we got to the homeless shelter we passed out the remaining 41 we had left. Next, we began making sandwiches and pairing them with other goodies(好吃的东西)and 42 them with the crowd. I had the cans with my sister’s cookies in them and began to walk around, offering them to anyone near me. I 43 an older gentleman and said, “Sir, would you like a 44 ?”He stopped and turned around, 45 ，“What did you say? Did you call me sir?” And I told him I had, and his eyes watered a little bit and he said, “No one has ever called me sir. 46 ” It 47 me to the core（彻底地）. I explained I had been taught that everyone deserved respect. It 48 me to think that just because he was homeless, no one afforded him the 49 which every person should get. It broke my 50 , and I couldn’t help but cry. I just didn’t understand 51 no one ever called him sir. Just because he didn’t have money or a place to live in. Every single person 52 to be treated with dignity(尊严). Years later, I 53 carry that memory and the lessons it taught me. Sometimes, what we take for granted as 54 gestures can really make a(n) 55 in someone’s life.
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