A．For i=1 To 4                                   B．For i=1 To 4

    n=1                                               For j=1 To i

    For j=1 To I                                              n=1

        n=n*j                                               n=n*j

    Next

    输出n                                              输出n

Next

C．n=1                                           D．以上三个都可以实现

    For j=1 To 4                                       题目要求的输出结果

     n=n*j

    Next

    输出n

A．i=5                                      B．i=1

  Do                                          Do

      i=i+1                                        i=i+2

  Loop While i＞0                               Loop While i≠10

  输出 i                                       输出i

C．i=10                                      D．i=6

  Do                                            Do

  i=i+1                                              i=i－2

  Loop While i＜20                                Loop While i≠1

  输出i                                          输出i

A．输入语句                                       B．输出语句

C．赋值语句                                       D．输入语句和输出语句

    输入a₁，a₂，a₃，…，a₂0；

i=1；a=0；b=0；c=0；

If a_i＞0 Then

    a=a+1

Do

    If a_i=0 Then

        b=b+1

    Else

        c=c+1

    i=i+1

Loop While  i≤20

输出a，b，c.

请改用For循环语句写出．