Operation & Maintenance操作与维修 Operations and Management操作和管理 Ohio and Mississippi Railroad俄亥俄州和密西西比的铁路 Operations and Maintenance操作和维护 Outline and Mounting轮廓和安装 Offshore & Marine海洋和海洋 Owens & Minor (Fortune 500 company)欧文斯和未成年人(《财富》500强公司之一) Organization & Methods组织的方法 Ozy & Millie (comic)Ozy和米莉(喜剧) Orientation & Mobility定位和机动性 Ogilvy & Mather奥美和妈妈 Operator & Maintainer经营者和维护者 Oceanography and Meteorology海洋和气象学的基本知识 Operations & Maintenance操作和维护 Original Equipment Manufacturer初始设备厂家