51. We started living here fifteen years ago. -We have.................................................... 52. You are a good student now,, he is a good student now (use neither) -You............................................................ 53. It isn't necessary for you to set off early. - You don't........................................................ 54. He failed the exam because of his laziness -Because he......................................... 55. I don't have enough time so I can't go out with you on Sundays -If I........................................................... 56. it's three years since I last spoke to her -I haven't.....................................................