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would it be correct to use(s) in the following scenerio?

There are two car air fresheners that someone has left on a table. Would it be correct to leave a note next to the air fresheners that reads : Put in your car(s)? Each person only has one car.

Thanks
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LOL
the sense would be clear which ever you used. Since, in English, there is no difference between the plural and singular form of "you" I would say that either would be fine, and not sound odd, as it might in a language where there is more pronoun variation,
(and more stress about "agreements"!)
Comments  
You only use ( s ) to make things plural when quantity is unclear. Since you know that everyone has only one car, you do not use ( s ).

BUT...

If one person owns one car and one person owns two cars, you could use ( s ) since you don't know who will read the note first.
 suzi's reply was promoted to an answer.