1.　　　 The ground __________ (下沉)to the sea.

30.　 t_________ a piece of work done as part of one’s duties, especially hard or unpleasant.

bined 20.vacation 21.poisoning/polluting 22.pronounce 23.survive 24.repeat 25.replace 26.sorrow. 27.board 28.exchange29.nature 30.task

Unit 4

29.　 n_________ the world of living things in the outdoors.

28.　 e__________ to give something that you have and get something different; trade

27.　 b__________ to get into a ship, or a plane, or any public vehicle.

26.　 s__________ a feeling of great sadness.

25.　 r________ to take, fill the place of

24.　 r______ to say, do, or experience again

23.　 s_______ to go on living, especially after coming close to death.

22.　 P_____ to make the sound of ( a letter , a word, etc.)