47.　　 He has no trouble ___________ (do) the job.

46.　　 It is used for ___________ (plant) trees.

45.　　 He is practice ___________ (speak) English.

44.　　 He is successful in　 ___________ (finish) the job.

43.　　 It has worked well in ___________ (help) them.

42.　　 They call for us ___________ (fight) against the pollution.

41.　　 He often encourage us　 ___________ (speak) English.

40.　　 Do you enjoy ___________ (listen) to the music?

39.　　 He has made contribution to ___________ (protect) the environment.

38.　　 You must pay attention to ___________ (look) after them.