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I've recently read that oxygen might be poisonous
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I recently read that oxygen might be poisonous
It's a sentence I'd like to use in common conversation with a friend.
Which one is correct grammatically and how to recognize that? I think the perfect would be better because I don't mean specified time and I don't give any details, but the past simple might be correct as well
Same question with
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I've thought this might be interesting. That's why I've brought it here.
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I thought this might be interesting. That's why I brought it here
Best Answer
Grammatically both of your first sentences are correct and idiomatic. One uses the present perfect, and the other uses the simple past. There's really no difference between them.
One might sound better than the other in the given context; for example if the other person used the present perfect to describe something, I might respond with a similar experience also using the present perfect.
Your second pair of examples is a little different. With the verb "to think" the present perfect indicates a past complete or repeated thought.
If you want to express an ongoing and current thought, the present perfect progressive is idiomatic:
Unfortunately this is more about what is natural in English, rather than grammar rules. You might have to figure out what is idiomatic on a case-by-case basic, as a set of common expressions.