【单选题】DNA 一条链片段 5 ' ATCG3 '另一条链:
【判断题】Three kinds of verb tenses are frequently used in English news headlines: present tense, future tense and present perfect tense.
【简答题】如图是某种汽车尾气处理装置中发生化学反应的微观示意图,请回答下列问题: (1)画出氮原子的结构示意图______,标出氨分子中氮原子的化合价______. (2)水分子中氧元素的质量百分含量为______.(保留一位小数)
【判断题】吸光光度分析不仅适用于溶液,也适用于任何于气体和固体。( )
【判断题】The present tense does not only mean what is true now. It can also refer to events in the past and the future.()