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质谱中质荷比最大的峰不一定是分子离子峰。( )
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仪器安装后必须确认没有短路等情况再行通电。( )
色漆、清漆产品的闪点测定范围在110℃以下。( )
Task 5Directions: Read the following passage. After reading it, you are required to read the questions and then complete the answers below them (No. 56 through No. 60). You should write your answers briefly on the Answer Sheet correspondingly. Scientists are trying to make the deserts into good land again. They want to bring water to the deserts so people can live and grow food. They are learning a lot about the deserts. Even so, more and more of the earth is becoming desert all the time. Scientists may not be able to change the deserts in time. Why is more and more land becoming desert Scientists think that people make deserts. People are doing bad things to the earth. Some places on the earth do not get very much rain. Yet they still do not become deserts. This is because there are some green plants growing there. Small green plants and grass are very important to dry places. Plants help keep water in the earth. Plants do not let the wind blow the dirt away. Without plants, the land can become a desert much more easily. A man decides to make a farm in a very dry place. He cuts down the trees. He digs in the earth and takes away the grass and plants that are already growing on the dry land. He makes a farm. He puts plants in rows. The sun is very hot. It makes the land even drier. When the rain comes, it runs between the rows of plants. It washes the good dirt away. When the wind comes, it blows between the rows of plants. It blows the good dirt away. Soon the land is not good enough for a farm anymore. The man lets his animals eat all the plants on it. Now the land does not have any plants on it. The sun and wind dry the land and blow all of the good dirt away. Now the land is a desert. What is mainly discussed in the passageHow more and more ____________________________.
质谱法分析气体可以多组分同时检测且一般不需要标准气。( )
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