以下程序的运行结果是( )。 Dim x As Integer, y As Integer, z As Integer Sub s1(a As Integer, b As Integer) Dim c As Integer a = 2 * a b = b + 2 c = a + b End Sub Sub s2(a As Integer, ByVal b As Integer) Dim c As Integer a = 2 * a b = b + 2 c = a + b End Sub Private Sub Command1_Click() x = 4:y = 4 :z = 6 Call s1(x, y) Print x + y + z Call s2(x, y) Print x + y + z End Sub