某VB程序段如下：

Dim i As Integer, n As Integer, k As Integer, s As String n = Val(Text1.Text)：k = 1: s = ""

Do While 2 ^k < n

    k = k + 1

Loop

Do While n <> 0

    If n >= 2 ^ (k -1) Then s = s + "1"

    n = n - 2 ^ (k -1)

    Else

        s = s + "0"

    End If

    k = k - 1

Loop

For i= 1 To k

    s = s + "0"

Next i

在文本框Text1输入12，执行该程序段后，变量s、k的值分别为（     ）

A、"1100"、2

B、"11"、2

C、"0011"、4

D、"1100"、4