单项选择题

在窗体上画一个命令按钮,然后编写如下事件过程:
Option Base 1
Private Sub Command1_Click( )
  Dim a
  a = Array(1, 2, 3, 4)
  j = 1
  For i = 4 To 1 Step -1
    s = s + a(i)* j
    j = j * 10
  Next i
  Print s
End Sub
运行上面的程序,单击命令按钮,其输出结果是________。

A.4321
B.12
C.34
D.1234