1. sit不及物动；坐；就座；
      sit—sat—sat—sitting
      例句：①He sat at the table writing a letter.(他坐在书桌旁写信。)
      ②Sit here until she comes back.(坐在这里等她回来。)

2. set安置；下沉；点燃；出考题；定时；树立(榜样)
      set—set—set—setting
      例句：①Tom, set the table for dinner.(Tom，摆好桌子准备吃饭。)
      ②He set the alarm for 6:00 in the morning.(他把闹钟定在早晨6点钟。)
      ③My teacher set very difficult questions for the exam.(我们老师试题出得非常难。)
      ④The sun rises in the east and sets in the west.(太阳从东方升起从西方落下。)

3. seat使坐；容纳
      seat—seated—seated—seating
      例句：①)The theater can seat at least 2000 people.(这家戏院至少能容纳2000人。)
      ②Please be seated.(请坐下。)此句等于Sit down please.
      ③He seated himself next to her.(他坐在她的旁边。)