II.
31. since
32. ago
33. since
34. ago
35. since
36. for
37. since
38. for
39. for
40.for

III.
41. Although
42. In spite of
43. In spite of
44. Although
45. Although
46. Because of
47. Although
48. Because of
49. Because 
50. Because of

IV.
51. took => take
52. studying => study
53. to smoke => smoking
54. a => an
56. because of => because
57. so much => so many
58. has been => was
59. because => because of
61. didn't watch => haven't watched
63. to listen => listening
64. in spite of => because of
65. watch => watching
66. to => of
67. will finish => finish
68. know => known
69. eat => have eaten

V.
76. Although it was cold, we went swimming.
=> In spite of the cold weather, we went swimming.
77. We stopped playing tennis because it started to rain.
=> Because of the rain, we stopped playing tennis.
78. Although he felt tired, he still went on working.
=> Despite his tired, he still went on working.