Prepositions“in, on, at”can be used as spatial prepositions as well as temporal prepositions. The temporal usages of“in, on, at”vary from each other in indicating different concepts of time. ESL students are often confused with the usages of tem⁃poral prepositions. This paper makes a comprehensive analysis of usages of“in, on, at”, aiming at distinguishing their befuddling usage principles and exploring the priority when their temporal usage principles are confronted with each other.
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