反转字符串，如输入字符串为“abcdefg”，则输出字符串“gfedcba”，实现该功能的部分程序如下所示，划线处的正确语句是（     ）

s = Text1.Text：n = Len(s)

'按s中字符顺序从左到右依次存入到数组a中，代码略

i = 1

Do While i <= n - 1

    t =  ①   

    For j = n - 1 To i Step -1

        a(j + 1) = a(j)

    Next j

      ②  

    i = i + 1

Loop

For i = 1 To Len(s)

    Text2.Text = Text2.Text +  ③   

Next i

A、① a(n)    ② a(j + 1) = t    ③ a(i)

B、① a(n)    ② a(j) = t    ③ a(i)

C、① a(i)    ② a(j + 1) = t    ③ Str(a(i))

D、① a(i)    ② a(j) = t    ③ Str(a(i))