题干

今年入夏以来,我国很多地区持续严重干旱,气象部门组织实施了多次人工降雨.在空中喷洒干冰是人工降雨的一种方法,干冰使空气中的水蒸气变成小冰粒,小冰粒在下降过程中变成雨滴,形成降雨.下列说法正确的是()

A:干冰使空气中的水蒸气变成小冰粒过程是凝固

B:干冰使空气中的水蒸气变成小冰粒过程是升华

C:小冰粒在下降过程中变成雨滴过程是汽化

D:小冰粒在下降过程中变成雨滴过程是熔化

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答案(点此获取答案解析)

D

同类题5

阅读下列短文,根据短文内容,从短文后各题所给的A、B、C、D四个选项中,选择最佳选项。

                                                                                       Bags of Love

      Last year, I worked in a middle school near my mother's house, and I stayed with her for a month. During that time, I helped her do some

 housework and buy some food.

      After the first week, I noticed that the food was eaten up very quickly. Then I began keeping an eye on my mum. To my surprise, I found

that she would put some of the food into a paper bag and go out with it at about nine every morning. And finally, I decided to follow her. I saw her taking the food to the street children. She would also spend a lot of time talking and playing with them.

      One day, I talked to a neighbour and found out that my mum was well-known in the area. The children were very friendly with her and even thought of her as their own mother. Then it hit me – why wouldn't she want to tell me about it? Was she worried that I would stop buying food if I found out?

  When my mum got home, I gave her a big hug (拥抱). I told her she didn't need to keep it a secret from me. And she told me something about the children. Some of them lived with an old lady in a small house. Others slept on the street. For years, she was helping the poor street children by giving them food. After she told me everything, I was so moved by how selfless (无私的) she was. She helped others in need. As her son, I was so proud of my mum.

      I continued to buy food for my mum after that. But I always added one more bag for her other children.