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did the train leave?I wanted to know. I wanted to know when the train left . there many people at the party?I didn’t know. I didn’t know if/whether there were many people at the party. it cost much money to fly to Beijing?Could you tell me? Could you tell me if/whether it costs much money to fly to Beijing? invented TV set?I don’t know. I don’t know who invented TV set. the girl need any help?He asked me. He asked me if/whether the girl needed some help.