【单选题】关于维生素A,下列叙述哪种是正确的
C.
维生素A有两种形式即A和A二者来源不同,但化学结构相同
【单选题】1927年8月1日爆发的哪一个起义打响了武装反抗国民党反动派的第一枪,标志着中国共产党独立领导武装斗争的开始?
【判断题】常见的统计量有样本均值、标准差、方差、原点矩、中心矩
【单选题】Is Continuing Ed for You? Continuing education is important for everyone now, in all fields. Almost as soon as you've completed a field of study and begun working--new ideas, approaches and techniques...
A.
you have to stay current in your discipline.
B.
new ideas and technologies are to be discussed.
C.
you have just completed your studies.
D.
you are just beginning to work.
【单选题】沉淀完成后不立即过滤,而是和母液一起放置一段时间。在此期间内发生的一切不可逆变化称为什么?