In most South American countries rail transport is plagued by operational problems as well as by obsolete equipment.
【正确答案】 B
【答案解析】解析：译文为：在大多数南美国家，铁路运输受到运营问题和过时设备的困扰。obsolete过时的。deficient不充分的；outdated过时的；inferior次等的；imperfect不完美的。