第18题: [单项选择]A. We cannot beat our competitors because of a staff shortage. B. We should be prepared to sign the business contract. C. We sometimes make a deal with one of our rivals. D. We are happy to see that our rival has gone bankrupt. 参考答案:B 答案解析:[听力原文] I believe our proposal is a real a contender for the contract. All we need to do is to
第24题: [单项选择]各种tRNA分子3′末端的最后三个核苷酸均是 A. CGA-OH B. CCA-OH C. AAC-OH D. UUA-OH 参考答案:B 答案解析:[考点] 核酸的结构
[分析] 各种tRNA的3′末端均具有统一的CCA-OH末端。该羟基可与氨基酸的羧基形成酯键,以使tRNA携带氨基酸。