H2</sub>C2</sub>O4</sub>的pKa1</sub>、pKa2</sub>分别为1.22、4.19。当溶液的pH=1.32时,溶液中的主要存在型体是()。
A.H2C2O4
B.HC2O4-
C.C2O42-
D.HC2O4-+C2O42-
A.H2C2O4
B.HC2O4-
C.C2O42-
D.HC2O4-+C2O42-
A. Pdvate Sub Commandl_click() CommonDialogl.DialogTitle="New Title" CommonDialogl.ShowPrinter End Sub
B.Private Sub Cormnandl_click() CommonDialogl.DialogTitle="New Title" CommonDialogl.ShowFont End Sub
C.Private Sub Commandl_click() CommonDialogl.DialogTitle="New Title" CommonDialogl.ShowOpen End Sub
D.Pfivate Sub Commandl_click() CommonDialogl.DialogTitle="New Title" CommonDialogl.ShowColor End Sub
A.Private Sub Command1_Click()
CommonDialog1.DialogTitle = "New Title"
CommonDialog1.ShowPrinter
End Sub
B.Private Sub Command1_Click()
CommonDialog1.DialogTitle = "New Title"
CommonDialog1.ShowFont
End Sub
C.Private Sub Command1_Click()
CommonDialog1.DialogTitle = "New Title"
CommonDialog1.ShowOpen
End Sub
D.Private Sub Command1_Click()
CommonDialog1.DialogTitle = "New Title"
CommonDialog1.ShowColor
End Sub
A.Private Sub List1_Click()
Label1.Caption = List1.ListIndex
End Sub
B.Private Sub List1_Click()
Label1.Name=List1.ListIndex
End Sub
C.Private Sub List1_Click()
Label1.Name=List1.Text
End Sub
D.Private Sub List1_Click()
Label1.Caption =List1.Text
End Sub
在窗体上画一个文本框(其名称为Text1)和一个标签(其名称为Labell),程序运行后,如果在文本框中输入指定的信息,则立即在标签中显示相同的内容。以下可以实现上述操作的事件过程是______。
A. Private Sub Text1 Click() Labell.Caption=Text1.Text End Sub
B.Private Sub Text1_Change() Labell.Caption=Text1.Text End Sub
C.Private Sub Labell_Change() Labell.Caption=Text1.Text End Sub
D.Private Sub Labell_Click() Labell.Caption=Text1.Text End Sub
窗体上有一个列表框,编写下列程序: Private Sub Command1_Click() ListRemoveItem3 End Sub Private Sub Form_Load() ListAddItem "拉瓦锡" ListAddItem "道尔顿" ListAddItem "汤姆森" ListAddItem "门捷列夫" End Sub 程序执行时,单击Commandd1,则在列表框中将不再出现 ______。
A.拉瓦锡
B.道尔顿
C.汤姆森
D.门捷列夫
A.Private Sub Commandl—click() Command2.ViSible=True Command3.ViSible=False End Sub
B.Private Sub Commandl_click() Command2.Enabl ed=True Command3.Enabl ed=False End Sub
C.Private Sub Commandl_C1ick() Command2.Enabled=True Command3.ViSible=False End Sub
D.Private Sub Commandl_C1ick() Coiihmand2.Vi s ible:True Command3.Enabled=False End Sub
A.Private Sub Form. Load() Show Text1.Text=" " Text2.Text=" " Text2.SetFocus End Sub Private Sub Text2_KeyDown(KeyCode As Integer,Shift As Integer) Text1.Text=Chr(KeyCode-4) End Sub
B.Private Sub Form_Load() Show Text1.Text=" " Text2.Text=" " Text2.SetFocus End Sub Private Sub Text2_KeyDown(KeyCode As Integer,Shift As Integer) Text1.Text=Text1.Text+Chr(KeyCode-4) End Sub
C.Private Sub Form_Load() Show Text1.Text=" " Text2.Text=" " Text2.SetFocus End Sub Private Sub Text2_Click(KeyCode As Integer,Shift As Integer) Text1.Text=Text1.Text+Chr(KeyCOde-4) End Sub
D.Private Sub Form_Load() Show Text1.Text=" " Text2.Text=" " Text2.SetFocus End Sub Private Sub Text2_Click(KeyCode As Integer,Shift As Integer) Text1.Text=Chr(KeyCode-4) End Sub