A. didn't tell B. hadn't told C. would not tell D. would have not told

【答案】B

【解析】句意：要是你没有告诉他我说的话就好了！ 一切都 会是顺利的。if only后应跟虚拟语气，句子用过去完成 时态表示对过去情况的假设。