Using coordination:We’ve told the landlord about the ceiling aga

Using coordination:
We’ve told the landlord about the ceiling again and again. He’s done nothing to fix the ceiling.
【正确答案】：We’ve told the landlord about the ceiling again and again, but he’s done nothing to fix it.
【题目解析】：But表示“但是，然而”，引出并列句。But是连词，连接一个句子，所以but总是位于所引出的分句之首。