【简答题】姜黄素(分子式为C 21 H 20 O 6 )具有搞突变和预防肿瘤的作用,其合成路线如下: 已知 ① ② 请回答下列问题: (1)D中含有的官能团名称 。 (2)试剂X为 。 (3)姜黄素的结构为 。 (4)反应D—E的化学方程式为 ,其反应类型是 。 (5)下列有关G(C 8 H 8 O 3 )的叙述不正确的是 (填正确答案编号)。 a.能与NaHCO 3 溶液反应 b.能与浓溴水反应 c.能与...
【简答题】听下面一段对话,回答第1-3小题。 1. What is the probable relationship between the speakers? A. Friends B. Classmates C. Co-workers 2. What does the man like to do? A. To cycle. B. To garden. C. To climb mountains. 3...
【单选题】The essence of systematic sampling is that:
A.
Each element of the population has an equal chance of being chosen
B.
Members of various strata are selected by the interviewers up to predetermined limits
C.
Every nth member of the population is selected
D.
Every element of one definable sub-section of the population is selected.
【单选题】The essence of systematic sampling is that:
A.
Each element of the population has an equal chance of being chosen.
B.
Members of various strata are selected by the interviewers up to predetermined limits.
C.
Every nth item of the population is selected.
D.
Every element of one definable subsection of the population is selected.
【单选题】从管理信息系统软件结构的角度出发,下列说法错误的是( )
【简答题】下列属于收货人(进口商)办理的业务的是A. 包装、储存B.签发多式联运提单 B. 签发多式联运提单 C. 安排报关和付税 D. 提货和付运费