I could get you a concert ticket. → I could not / couldn't get you a concert ticket.
I was on the Internet when you called me. → I was not / wasn't on the Internet when you called me.
【技巧3】当句中谓语是除情态动词、助动词、系动词was,were以外的动词时，在该动词之前加did not / didn't，动词还原，构成否定句。例如：
The famous singer sang some Chinese songs. → The famous singer did not / didn't sing any Chinese songs.
He could pack his things himself. → Could he pack his things himself?
Mr Li looked very old. → Did Mr Li look very old?
【技巧1】确定疑问词：人who / whom，物what，地点where，时间when / what time，原因why，频率how often，长度how long，距离how far等等。例如：
They gave the concert last night. → When did they give the concert?
【技巧2】辨认结构形式：疑问词+情态动词/助动词/ was / were / did +主语+...? 例如：
The accident happened near the station. → Where did the accident happen.