红霉素的抗菌机制是（）
A.抑制RNA多聚酶
B.抑制二氢叶酸还原酶
C.抑制转肽作用及（或）mRNA移位
D.与青霉素作用机制相似
E.与细菌核蛋白体的30S亚基结合，而阻碍蛋白质的合成
参考答案：C
解析：红霉素与核蛋白体50S亚基结合，抑制肽酰基转移酶的转肽过程，通过从空间上阻滞新生肽链的延伸和促进pt-tRNA的脱落而起抗菌作用。
根据短文内容，从下框A~F选项中选出能概括每段主题的最佳选项，选项中有一项为多余项。
小题2:You cannot have success if you don’t know what it means to you. Set clear goals and be realistic. Your standards should be specific or else you will spend your entire time chasing after a vague goal. For example, you want to be good at your job. However, this is not a specific goal. Instead, specify this goal as: “My goal is to only be late for work five times per year, at the most.” This is a specific goal that when achieved, give you a sense of satisfaction and completion, making you feel successful and confident. 小题3:Successful people think big and act big. It can be scary to do, but if you don’t, then how will you ever be successful? Don’t wait for opportunities. Dig them out. Successful people make big investments (in their careers, in their business, in their education) and all investments involve some degree of risk. Study your risks, and be brave. 小题4:People who are successful like solving problems and answering questions. No matter where you are or what you are doing, look around and try to think of ways you can find, for example, what are people struggling with or complaining about? How can you make life easier for them in an effective way? Can you redesign or reorganize some aspects of the situation so that things can run more smoothly? 小题5:You should learn to persist. It is also the key factor to success. When asked about his 10,000 failed attempts to develop a storage battery, the prolific（多产的）American inventor Thomas Edison replied: “I have not failed; I’ve just found 10,000 ways that won’t work. So, if your first attempt didn’t work, don’t quit and don’t give up.” |