We should bear in mind that social development and balance of nature should go  in         .  

The workmen made so much _____ that Mrs. Walker had to spend three days cleaning up afterwards.

The boy led his mother to the ________ of the accident.

----What do you know the _____ of are the pig influenza in humans? ---- usually similar to regular human seasonal influenza .

  Lu Xun said, “ The ____ were made by people.”