Dim a(1 To 100)As Integer

n=Val(Text1.Text)

a(1)=0：a(3)=1

s=1

Next i

Text2.Text=Str(s)

方框中的代码由以下三部分组成：

①a(i)=a(i-2)+a(i-4)
②s=s+a(i)

③For i=5 To n Step 2

代码顺序正确的选项是(  )

s=0

For k = 3 To 1 Step -1

   If k <= 1 Then x = 1

   If k <= 2 Then x = 2

   If k <= 3 Then x = 3

   s = s + x

Next k

该程序段运行后，变量 s 的值是（    ）

Private Sub Command1_Click()

    Dim Pi As Single, t As Single

    Dim n As Integer, s As Integer

    Pi = 0

    t = 1: n = 1: s =1

    Do While Abs(t) >= 0.0001

        Pi = Pi + t

        n ={#blank#}1{#/blank#}

        s= {#blank#}2{#/blank#}

        t = s / n

    Loop

    Text2.Text ={#blank#}3{#/blank#}

End Sub

⒈能被4整除，但不能被100整除；

⒉能被400整除；

que=[""]*20

head,tail= 0,0

for i in range(3):

    que[tail]=chr(97+i)

    tail+= 1

st=["b","c","d","a"]

top=3

while head < tail and top > - 1:

    if st[top]==que[head]:

        head+= 1

    else:

        que[tail] = st[top]

        tail+= 1

    top-= 1

print(que[head:tail])

执行该程序段，则输出的结果是(  )

a = [ 5 , 4 , 2 , 1 , 3 , 6 ] ; q = [ 0 ] * 6 ; head = tail = 0

for i in range( len( a ) ):

    if a[ i ] % 2 == 1 :

        q[ tail ] = a[ i ] ; tail = tail + 1

    elif head < tail :

        head += 1

print( tail – head )

执行该程序段后，输出结果为（   ）