在窗体上画一个名称为Command1的命令按钮和三个名称分别为Label1、Label2、Label3的标签，然后编写如下代码： Private x As Integer Private Sub Command1_Click() Static y As Integer Dim z As Integer n = 10 2 = n + z y=y+z x = x + z Label1.Caption =x Label2.Caption =y Label3.Caption =z End Sub 运行程序，连续三次单击命令按钮后，则三个标签中显示的内容分别是

A) 10 10 10
B) 30 30 30
C) 30 30 10
D) 10 30 30