Dim a(1 To 5) As Integer

a(1) = 1

For i = 2 To 5

    a(i) = Int(Rnd * 5) + 1

    If a(i) Mod 2 = 0 Then

         a(i) = a(i) + i

    Else

        a(i) = a(i) + a(i - 1)

    End If

Next i

a(1)~a(5)的值不可能的是（   ）

Private Sub Command1_Click()

    Dim s As String, s1 As String, c As String

    s = Text1.Text

    For i = 1 To Len(s)

        c = Mid(s, i, 1)

        s1 =    ⑴   

        For j =    ⑵   

            If c <> Mid(s, j, 1) Then

                s1 = s1 + Mid(s, j, 1)

            End If

        Next j

           ⑶    

    Next i

Text2.Text = s

End Sub

s1="today"

s2=""

for c in s1:

    s2=c+s2

print(s2)

a=[["迎客松" , 21, 2],["激流勇进" , 40, 2],[" 天空栈道" , 50, 5],["一线天" , 30, 4],[" 飞来 峰" , 60, 5],["天梯" , 20, -1]]

head=[0, 1, 3]

for i in range（len（head））：

       ⑴     

    s=a[p][1]

    while a[p][2]! =-1：

        print（a[p][0], end="-->"）

            ⑵   

           ⑶    

    print（a[p][0]）

    print（"预计时间：" , s , "分钟"）

上述程序划线处的可选代码有：

①p=head   ②p=head[i]    ③s=s+a[p][1]    ④p=a[p][2]

则（1）,（2）,（3）处代码依次为：（   ）