Const n = 6

Dim a(1 To n) As Integer, f(1 To 10) As Boolean

Dim tmp As Integer, i As Integer, j As Integer, t As Integer

‘f数组各元素的初值置为False，代码略

For i = 1 To   ⑴ 

    t = Int(1 + Rnd * 10)

    If Not f(t) Then

        a(i) = t : f(t) = True

        For j =   ⑵ 

            If a(j) < a(j - 1) Then

                tmp = a(j): a(j) = a(j - 1): a(j - 1) = tmp

            End If

        Next j

    Else

      ⑶ 

    End If

Next i

上述程序段3个方框处的表达式分别为(   )

s = "abcxyz"

q = [1,2,3] + [0] * 10

head , tail = 0 , 3

res = ""

for i in s :

    c = chr ((ord(i) - ord("a") + q [head]) % 26 + ord("a"))

    res += c

    q [tail] = q [head]

    head = head + 1

    tail = tail + 1

print(res)

执行该程序段后，输出的结果是（   ）