反转录酶的作用是（） A.催化多肽链的合成 B.直接参与基因表达调控 C.可作为分子 发布时间：2018-01-28 07:31 │ 来源：www.tikuol.com 题型：单项选择题 A1型题 问题： 反转录酶的作用是（）A.催化多肽链的合成B.直接参与基因表达调控C.可作为分子生物学的工具酶D.催化以RNA为模板合成RNAE.参与氨基酸代谢
题型：单项选择题 A1型题 完形填空。 Friends are important in our life. But first, you have to decide what kind of friends you want to 1 . My ideal (理想的) friend is of course a good friend whose goodness is shown below - he has no badlikings, such as smoking and drinking. He lives in frugality (节俭). He studies hard so as not to 2 his golden time. At home he honors his parents and loves his brothers. At school he 3 his teachers and shares feelings with his classmates. He treats those who 4 true to him honestly. In a word, he has allthe good characters 5 than mine. I can follow him as a model. 6 his help, I am free from alldifficulties. Indeed, if I have such a person as my friend, I shall never be afraid of 7 and I shall never knowthe existence (存在) of the word "failure". ( )1. A. offer ( )2. A. afford ( )3. A. respects ( )4. A. is ( )5. A. good ( )6. A. With ( )7. A. success B. have B. remind B. hates B. was B. well B. At B. difficultyC. recognize C. find C. annoys C. are C. best C. Through C. freedom D. talk D. waste D. listens D. does D. better D. To D. darkness 查看答案
题型：单项选择题 A1型题 某企业生产甲、乙两种产品，已知生产每吨甲产品要用A原料3吨、B原料2吨；生产每吨乙产品要用A原料1吨、B原料3吨，销售每吨甲产品可获得利润5万元、每吨乙产品可获得利润3万元，若该企业在一个生产周期内消耗A原料不超过13吨、B原料不超过18吨，那么该企业可获得最大利润是[ ]A.20万元 B.25万元 C.27万元 D.30万元 查看答案