I need some help with basic grammar.
What is the difference between these sentences:
Thank you in advance!
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I'm only learning myself so I'm not sure, but I think all sentences are correct, since "真面目な/真面目だった" are both the present/past prenominal forms of "真面目", and I don't think these collide in any way with the です/でした copula at the end of the sentence.
1.これは真面目だった人です。 This is a person who used to be serious.
2.これは真面目な人でした。 This was a serious person.
3.これは真面目だった人でした。 This was a person who used to be serious (but that changed at some point).