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Using the three prepositions (in/on/at) when their use is related to the word after them is very confusing to learners.
E.g. in these examples all the prepositions refer to a location:
The players were on court for three hours
Do you feel sleepy at school or at work?
Originally found in all countries
Also, the three prepositions are used to refer to a time like on the weekend, at 7 AM and in the morning.
Is there an easy way to tell which one is correct to use? If not, can someone please lead me to where (a website) I can learn to use them correctly?