【单选题】Why is Tambora mentioned in this clip?
A.
To remember the people wh died in that event.
B.
To show how powerful volcanoes are.
C.
To warn people to stay away from Tambora.
D.
To show how weak people were at that time.
【单选题】Why is Tambora mentioned in this clip?
A.
To remember the people who died in that event.
B.
To warn people to stay away from Tambora.
C.
To show how powerful volcanoes are.
D.
To show how weak people were at that time.
【单选题】实体完整性要求主属性不能取空值,这一点可以通过( )来保证。
【简答题】阅读以下应用说明及Visual Basic部分程序代码,将应填入(n)处的字句写在对应栏内。 【说明】 该应用程序是用来修改文本框中的字体属性,其运行窗口如图4所示。 窗口由1个标签(Labell)、1个文本框(txtPassage)和4个选择框(chkFont,chkltalic,chkSize,chkColor)组成。程序运行后,用户在文本框内输入一段文字,然后按需要单击各选择框,用以改变文本...
【单选题】关系数据模型中用来保证实体完整性的是______。
【单选题】实体完整性规则要求主属性不能取空值,为此,可通过______来保证。
【简答题】词形变化。 1. Why not go _________(boat) on the river with me? 2. The children like _______( swim) in the lake. 3. Do you enjoy _______(teach) English in our class, Mr. Green? 4. Are you ______(go)______(h...
【单选题】实体完整性要求主属性不能取空值,这一点通常是通过( )。