58. two-thirds of the work has been finished

57. is covered with snow all year round

56. are (must be) shut down when you leave

55. so that they could finish the work soon

54. of others than himself

53. he is no longer alive, his spirit lives

52. is one of the best I've read

51. be more careful from now on

50. less dangerous than

49. be done to stop this kind of accident from happening