单项选择题

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