the sentence to fix was

i've been to china last year.

i fixed it by writing "I went to china last year"

i have to explain the error, in my gramar book it says, you cannot use I've been with a specific time reference.
why cant you ?
is this true?
please help?
You're right to be confused. The grammar book is wrong. You can, for example say "I've been in China for five days, thirteen hours, forty minutes, and twelve seconds." Is that specific enough? To give the book some credit, although specificity isn't the issue, time is. The present perfect tense ("have been") describes action that is now complete. So as long as your specific time reference includes the present, you're fine. If, however, the action was completed in the past, you would use the past perfect tense ("I had been to China for a month in 1983, but my memories of it were still vivid.") or simply the past tense ("I was in China last year.").
treat present-perfect as indefinite-past(past without a definite time point/interval).
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enkatesu, can you please explain that better
Bet he can't.