observer

n.观察者，观察员；评述者

obscene, obscenely, obscenity, obscur, obscure, obscurely, obscurity, obsequies, obsequious, obsequiously, obsequiousness, observable, observance, observant, observantly, observation, observation car, observation post, observatory, observe, observing, obsess, obsessed, obsession, obsessional, obsessive, obsessively, obsolescence, obsolescent, obsolete, obssess, obstacle, obstacle race, obstetric, obstetrician, obstetrics, obstinacy, obstinate, obstinately, obstreperous,