题目

   A group of graduates got together to visit their old university professor.They talked about the 36    topic-happiness.But soon their conversation turned into complaints about  37  in work and life. To offer his guests coffee, the professor went to the kitchen and  38  with a large pot of coffee and a variety of  39  plastic,glass, metal, porcelain (陶瓷), som  plain-looking  some  very  40  .The professor told his students to help themselves to hot coffee.     When all the students had a cup of coffee in  41  . the professor said:lf you have noticed, all the东非裂谷带地质构造属于（  ） A、向斜  B、背斜  C、褶皱山 D、断层