knock at

• Have you ever thought of trying knocking at the back door
  你想过试着敲敲后门了吗？
• While he was watching tv , he heard a knock at the door
  当他看电视时，听到了敲门声。
• We were having dinner when someone knocked at the door
  我们正吃晚饭，突然有人敲门。
• He was having dinner when someone knocked at the door
  他正在吃午饭，突然有人来敲门。
• When someone knocked at the door , we were having supper
  有人敲门时，我们正在吃晚饭。
• Somebody s knocking at the door . i ll answer it
  有人在敲门，她太瘦了。
• There ' s a knock at it ' s the dustman . the door . who ' s it
  是清洁工。有人在敲门。谁呀？
• Somebody s knocking at the door . i ll answer it
  有人在敲门，卖身还债他每天去上班。
• The doctor ' s naughty daughter knocked at the locked door
  医生淘气的女儿敲着锁着的门。
• I reached the house , and knocked at the kitchen - door
  我到了房子跟前，敲了敲厨房的门。