实验Ⅰ：称量镁条，在空气中点燃，待反应结束后，将生成物全部收回再称量．

实验Ⅱ：将装有稀盐酸的小试管放入装有锌粒的烧杯中，称量，然后将盐酸与锌粒接触，过一会在称量。

实验Ⅲ：将装有氢氧化钠溶液的试管放入盛有硫酸铜的锥形瓶中，并在锥型瓶口塞上橡皮塞，称量，然后设法将两种溶液接触（有蓝色氢氧化铜沉淀和硫酸钠生成）过一会再称量。数据见下表：

小刚同学站在竖直放置的平面镜前5m处，向平面镜的方向前进了2m , 此时他在镜中的像与他本人的距离为（）

如图已知圆的半径为$10$，其内接$△ABC$的内角$A$，$B$分别为${60}^{°}$和$45°$，现向圆内随机撒一粒豆子，则豆子落在$△ABC$内的概率为（  ）

    Many years ago, when we first went to Canada, we were driving through Montana to Colorado with our two children, then aged 8 and 11. As it was getting1we started looking for a hotel, only to find out that it was

    2time in that part of the country, and all the hotels were3.

Finally, around 9 o'clock in the evening, we 4 at a gas station to fill up on gas. My husband asked for a

    5 book and told the woman at the counter that we were trying to find a hotel. She told us it would be 6. He tried for 15 more minutes. When he was 7, the woman, Linda, said she and her family

     8 nearby and would be happy if we spent the night at her home.

My husband was 9 at her offer of generosity (慷慨). She called her son to10us, since she had to

    11 at the gas station till midnight.

    When we reached their home, her husband12 us. He invited us to have coffee and chat while we 13 his wife. She came past 12 am. We asked if we could slip away in the morning so as not to14 them. They said we were now 15 and we would have to have breakfast with them.

    Next morning, we ate breakfast, and when we were 16, my husband asked if he could offer some17. They would not hear of it and18we were their guests. We kept in touch for many years, and invited them to our19, too. Over the years, we lost touch, but have 20 forgotten their kindness.