预防支气管哮喘发作首选哪种药物：
A．麻黄碱
B．沙丁胺醇
C．异丙肾上腺素
D．阿托品
E．肾上腺素
参考答案：A
解析：预防支气管哮喘用药。沙丁胺醇口服有效，作用可维持4～6h，而且有明显的β受体选择性，其舒张支气管作用较强，故用于支气管哮喘发作的预防。这种考虑完全正确，但本题所问预防支气管哮喘发作首选药物，选项中A项麻黄碱更具优点，因为麻黄碱作用出现缓慢、温和、持久更适宜预防给药。同时麻黄碱不但激动β受体，且激动α受体，可使支气管黏膜血管收缩，减轻水肿，有利于气道畅通。
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| But 1 a few of them are very 2 . English is one of these. Many, many people use it, not only in England and the U. S. A, but in other parts of the world. About 200, 000, 000 speak it as their own language. It is difficult to say how many  people are learning it as a 3 language. Many millions are 4 to do so. Is it easy or difficult to learn English? Different people may have different 5 . Have you ever 6 the ads of this kind in the newspapers or magazines? 'Learn English in six month, or your 7 back ...' 'Easy and funny? Our records and tapes 8 you master your English in a month. 9 the first day your 10 will be excellent. Just send ..." Of course, it never 11 quite like this. The only language that seems easy to learn is the mother tongue. We should 12 that we all learned our own language well when we were 13 . If we could learn English in the same way, it would not seem so difficult. 14 what a small child does. He listens to what people say. He tries what he hears. When he is using the language, talking in it, and 15 i  n it all the time, just imagine how much 16 that gets! So it is 17 to say that learning English is easy, because a good command of English 18 upon a lot of practice. And practice needs great effort and 19 much time. Good teachers, records, tapes, books, and dictionaries will 20 . But they cannot do the student's work for him. | |||
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