有如下 VB 程序段：

s = Text1.Text

If Mid(s, 1, 1) = "(" Then flag = True Else flag = False

cnt = 0: sum = 0

For i = 2 To Len(s)

  c = Mid(s, i, 1)

  If flag = True Then

    If c >= "a" And c <= "z" Then

      sum = sum + 1

    Else

    If sum <> 0 Then cnt = cnt + 1: sum = 0

    End If

  End If

  If c = "(" Then flag = True

  If c = ")" Then flag = False

Next i

文本框Text1的内容为一串只包含小写字母、左右括号和空格的字符串“(we can) do (better) we (should (be )better)”，执行程序段后，变量cnt的值为（   ）

A、3

B、4

C、5

D、6