obstacle

n.障碍，妨碍

observance, observant, observantly, observation, observation car, observation post, observatory, observe, observer, observing, obsess, obsessed, obsession, obsessional, obsessive, obsessively, obsolescence, obsolescent, obsolete, obssess, obstacle race, obstetric, obstetrician, obstetrics, obstinacy, obstinate, obstinately, obstreperous, obstreperously, obstreperousness, obstruct, obstruction, obstructionism, obstructionist, obstructive, obstructively, obtain, obtainable, obtrude, obtrusion,