题目: Tom is an honest boy, _____ he told a lie this time.[ ]A. but B. however C. though D. so 答案: 答案:B
题型:计算题 “化学为生命密码解锁”,“DNA”承载着生命遗传的密码,胞嘧啶(C4H5ON3)是DNA水解产物之一.(1)胞嘧啶中碳、氢、氧、氮四中元素的质量比为 (2) g胞嘧啶中含32g氧元素? 查看答案