通过抑制RNA逆转录酶而终止病毒DNA链的延伸的是（）
A.两性霉素B
B.氟胞嘧啶
C.灰黄霉素
D.利巴韦林
E.齐多夫定
参考答案：E
解析：灰黄霉素的抗菌机制主要通过干扰真菌核酸合成而抑制细菌的生长；齐多夫定的抗菌机制：抑制RNA逆转录酶而终止病毒DNA链的延伸；两性霉素B：抑制真菌细胞膜麦角固醇的合成，改变细菌通透性而导致细胞死亡；氟胞嘧啶的抗菌机制：在真菌细胞内转化为氟尿嘧啶，阻断核酸合成；利巴韦林的抗菌机制：抑制病毒的三磷酸鸟苷合成，抑制病毒mRNA合成。
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| Americans spend their weekends in different ways. But usually they choose the same aim (目的) to rest, to 1________ beautiful places and to enjoy the time with their 2________ and friends. Some Americans hold parties on Saturday night. They will dance, sing and drink together till midnight. They won't get up 3________ 9 or even 11 o'clock next. morning. As 4________ as they get up they will go to the nearest shop to buy the daily newspaper. They can get news about films, plays, shows and sports in the newspaper. It will help them to decide 5________ to do on Sunday afternoon. Before 6________ 0ut on Sunday, they will have a meal, which is 7________ "brunch" ------ "br" from 8________ and "unch" from "lunch". They will make it at home to go to a nearby restaurant. After brunch some Americans may have a picnic. They will take many things with them, such as fruit, vegetables and so on. Sunday dinner i.s the most 9________ meal of the week. It is the biggest meal of the week and all family members try to be present. Weekends are to be welcome 10________ .Most people hope for them. 1. ________ 2. ________ 3. ________ 4. ________ 5. ________ 6. ________ 7. ________ 8. ________ 9. ________ 10. ________ |