Set 6 Answer.
41) hidden

42) quietest

43) occasional

44) silence

45) peaceful

46) character

47) known

48) seems

49) say

50) frequently

51) impossible

52) depth

53) plants

54) temperature

55) cold

56) rises

57) night

58) hunting

59) seals

60) breathe

61) wait

62) air

63) shooting

64) holes

65) those

66) Despite having studied the language for two years, Roger cannot write in French.

67) Each of the girls has donated generously to the charity event.

68) Sally asked me if I wanted to use the telephone.

69) The lugguage will not be transported before the customs officers have checked them.

70) Derek did not buy the laptop due to his dissastisfaction with the salesman's service.

71) He had a good view of his surrounding and could see anyone approaching.

72) It was the sound of an aeroplane.

73) There was no shelter for him to hide from his enemies.

74) The writer had seen one of the two men looking at him through his binoculars.

75) It refers to the writer having the opportunity to escape from his enemies.

76)He wanted to make himself look like a real roadman and he also did not want the two men to recognise him.

77) He did not look up as they came near him.

78) The sentence is "I saw two pairs of eyes that missed nothing.".

79) The writer's boots were not those which people who lived in the countryside would wear.

80) They came back ten minutes later to check on him.