问题
单项选择题
二、配伍选择题
具有升华性的是( )
A．小檗碱
B．麻黄碱
C．甜菜碱
D．槟榔碱
E．咖啡因
答案
参考答案：E
解析：[知识点] 生物碱的性状
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二、配伍选择题
具有升华性的是( )
A．小檗碱
B．麻黄碱
C．甜菜碱
D．槟榔碱
E．咖啡因
参考答案：E
解析：[知识点] 生物碱的性状
When you speak, write a letter or make a telephone call, your words carry a message. People communicate (交流) with words. Do you think you can communicate without words? A smile on your face shows you are __1__ . Tears in your eyes tell others you are sad. When you __2__ your hands in class, the teacher knows you want to __3__ something or ask questions. You __4__ your head from side to side, and people know you are saying no. Other things can also carry messages. For example, a sign at the __5__ helps you know which bus you can take here. A sign on the wall of your school helps you __6__ the library. Signs on the doors tell you __7__ to go in or out. Have you ever noticed that there are lots of signs round you and that you receive messages __8__ them all the time? Books, newspapers, TV, radios and __9__ all help us to communicate with other people. They all help us __10__ what is going on in the world and what other people are thinking about.
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