Some people remember the things by writing notes to themselves. Then they leave the notes in obvious  places, such as on the table or on the floor in the middle of the living room. I don't think I like to write notes to myself. Most of the time I lose them or forget to look at them until it's too late. I prefer to use an alarm clock to tell me what I should do. I have ten alarm clocks in my house. They could tell me about things. For example, if I have to make a telephone call at a certain time, I'll set an alarm clock to go off a few minutes early and put the clock by the telephone. Or if I want to watch a certain television program, I'll set an alarm clock at the right time and put the clock on top of the TV set. I can remember almost anything if I use my clocks. However, sometimes an alarm clock goes off and I don't know what it means. I always remember setting it, but I do not know why I set it. If the clock is by the telephone, I know I may have set it to tell me to call someone, but I can't be sure. I might have set it to tell myself that somebody was to call me at a certain time. In this passage, "go off" means   _  .
start off get off go away make a sudden noise