For i = 1 To 2

        For j = 2 To 7 - i

            If a(j) > a(j - 1) Then

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

            End If

        Next j

Next i

数组元素a(1)到a(6)的值依次为“71，54，58，29，31，78”，经过该程序段“加工”后，下列说法正确的是（   ）

For i= 1 To 2

    For j=5 To i+1 Step-1

      If a(j) >a(i) Then

        t=a(j)：a(j)=a(i)：a(i)=t

      End If

    Next j

Next i

数组元素a(1)到a(5)的值依次为“33，24，45，16，77”，经过该程序段“加工”后，数组元素a(1)到a(5)的值依次为（  ）

For i= n To 2 step -1

  For j =

    If a(j) > a(j + 1) Then

      t = a(j): a(j)=a(j + 1): a(j + 1)=t

    End If

  Next j

Next i

方框中的代码会是以下四句中的某一句：

① 1 To i -1                ② n–1 To i Step -1

③ 1 To n - i                ④ n–1 To n - i+1 Step-1

正确的选项是（    ）

m = (1 + n) \ 2       ‘n为数组元素的个数，m为数组中间位置元素的下标

For i = 1 To n

    If a(i) < a(m) Then t = a(i): a(i) = a(m): a(m) = t

Next i

p = m: q = m

For i = 1 To n - 2

    If i Mod 2 = 1 Then

        k = q + 1: q = q + 1

    Else

        k = p - 1: p = p - 1

    End If

    pos = k

    For j = 1 To n

        If And a(j) < a(k) Then k = j

    Next j

    If pos > k Then

        t = a(pos): a(pos) = a(k): a(k) = t

    End If

Next i

上述程序段方框处的代码为（  ）

Dim a(1 To 5) As Integer

Randomize

a(1)=2：a(2)=6：a(3)=9：a(4)=3：a(5)=4

For i=1 To 4

    For j=1 To 5-i

        If a(j)+Int (Rnd*2)< a (j+1) Then

            k=a(j)：a(j)=a(j+1)：a(j+1)=k

        End If

    Next j

Next i

执行该程序段后，a(1)~a(5)的值不可能是(    )

s = input()

head = 0; tail = 0; ans = 0; tmp = '' q = ['']*100

flag = True

for i in range(len(s)):

    if s[i] == ',':

        while head!=tail:

            tmp += q[head]

            head += 1

            if flag and head < tail:

                head += 1

            flag = not flag

        ans += int(tmp)

        tmp = ''; flag = True

    elif '0'<=s[i]<='9':

        q[tail] = s[i]

        tail += 1

 若输入 s 为“1-500,2023900-,”，执行该程序段，变量 ans 的值为 （   ）