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on.abbr.=octane number 【化】辛烷值onprep.在 ... 之上；由 ... 支撑着；在（某一天）；关于；基于adv.穿着；向前（移动)；表示持续性adj.表示已连接、处于工作状态或使用中；发生；值班on - line sweeping technique在线推扫富集技术On Expressive Forms of Culture试论文化的表现形式onychia superficialis undulata[医] 浅纹甲On the Feudal Landlord Economy论地主经济On Language Relevance in Texts论语篇中语言的关联性on-line data handling system直接数据处理系统On Ownership of Uptown Garages略论住宅小区车库的权属ON PURE ARCHIMEDEAN SEMIGROUPS关于纯阿基米德半群ON THE LIABILITY WITHOUT FAULT论无过失责任on site bus controlling system现场总线控制系统

1. The sentry was ordered to shoot on sight.
   哨兵奉命一发现目标就射击。
2. The guard had orders to shoot on sight.
   哨兵奉命见人就开枪。
3. The sentry had orders to shoot on sight.
   哨兵奉命一发现有动静就立即开枪。