50. When I________for my sister in front of the supermarket, a strange man came to talk with me. A. was waiting B. waited C. had waited D. were waiting 51. Over the past 30 years, the average robot price________by half in real terms, and even further relative to labor costs. A. is fallen B. has fallen C. were fallen D. have fallen 52. When I came to visit her last night, she________a bath. A. is having B. was having C. has had D. had had 53. John________in the same house since he left school. A. lived B. had lived C. was living D. has lived 54. Since Tom________, I have heard nothing from him. A. had left B. left C. has left D. was left 55. He will take the dog out for a walk as soon as he _______ dinner. A. finish B. has finished C. will finish D. finished 56. John..tennis once or twice a week. A. is playing usually B. is usually playing C. usually plays D. plays usually 57. Tom.his hand when he was cooking dinner. A. burnt B. was burning C. has burnt D. had burnt 58. Everything is going well. Weany problems so far. A. didn't have B. don't have C. haven't had D. hadn't had 59. Jane.just a few minutes ago. A. left B. has left C. leaves D. had left 60. When I was a child, I used tothe violin. A. was playing B. am playing C. played D. play