For i = 1 To 9 Step 2

  b(a(i) Mod 10) = b(a(i) Mod 10) + 1

Next i

s = 0

For i = 0 To 9 Step 3

  s =s + b(i)

Next i

数组b各元素初始值为0， 数组元素a(1)到a(9)的值依次为“29,74,12,38,16,45,21,57,33”,则执行该程序段后，s的值为（  ）

count=0

For i=1 To 20

    a(i) =Int(Rnd*100) + 1

Next i

For i= 1 To 20

    ①

Next i

For i= 1 To 100

    If b(i) <> 0 Then count =count+1

Next i

Label 1.caption=“不重复数字个数”+Str(count)

为实现上述功能，则程序①处应填入的语句为（  ）

Private Sub Command1_Click()

    Dim a As Integer, b As Integer

    Dim c As Integer                     '①

    a= Val(Text1. Text)                     '②

    b = Val(Text2. Text)

    c=a + b                             '③

    Label1. Caption ="a + b="+c        '④

End Sub

from random import randint

res=" "

i,j=0,len(s)-1

while i<len(s) and j>=i:

    if randint(0,1) == 0:          #randint(0,1)随机生成 0 或 1

        res+=s[i]

        i+=1

    else:

        res+=s[j]

        j-=1