单项选择题

单击命令按钮时，下列程序段的执行结果为( )。
Private Sub Command1_Click()
Dim a As Integer, b As Integer, c As Integer
a-2:b=4:c=6
Call S1(a, b)
Print "a="; a; "b="; b; "c="; c
Call S2(a, b)
Print "a ="; a; "b="; b; "c="; c;
End Sub
Private Sub S1(x As Integer, y As Integer)
Dim c As Integer
x=2*x:y=y+2:c=x+y
End Sub
Sub S2(x As Integer, ByVal y As Integer)
Dim e As Integer
x=2*x:y=y+2:e=x+y
End Sub