在液相色谱中,为了改变柱子的选择性,可以进行下列哪种操作。( )
A. 改变柱长;
B. 改变填料粒度;
C. 改变流动相或固定相种类;
D. 改变流动相的流速。
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Focusing on the main ideas and complete the following paragraph with key information from the text.One day, at the registrar’s office of a college, I noticed how parents are behaving with their college-age children nowadays. Obviously students are young1 and can handle registration by2 , but their parents completely3 the situation. In a seminar for teaching assistants, I was surprised to hear that parents often go to their office to4 about marks and assignments their children have got. What I have seen and heard has left me feeling 5. Unlike my parents allowing me to make6 in my life, parents of today’s college students seem never to give their children a chance to take7 .
以下是元素作用的是()。
A. 该元素用来定义文档类型
B. 该元素用来声明命名空间
C. 该元素用来向搜索引擎声明网站关键字
D. 该元素用来向搜索引擎声明网站
下列关于CSS的说法错误的是()。
A. CSS的全称是CascadingStyleSheet,中文含义是“层叠样式表”
B. CSS的作用是精确定义页面中各个元素以及页面的整体布局
CSS样式不仅可以控制大多数传统的文本格式属性,还可以定义一些特殊的HTML属性
D. 使用Dreamweaver只能可视化定义CSS样式,无法以源代码方式对其进行编辑
在CSS中,ID选择器在定义时前面要有指示符()。
A. *
B. .
C. !
D.