In Seoul, Korea it’s said that the air pollution is bad and that it shortens people’s lives by a year or so, would this be true for someone who is going to visit only for three months??

yes

Explanation:

I would say it would be true because even though you are visiting for 3 months you will still be breathing the polluted air for the 3 months thus it would affect a person in a negative way and it is true.

b.) plain  

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