The film has been on ( ) 20 minutes. (for, since)
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Mr. Green has worked here ( ) he came to China. (for, since)
His grandparents have been dead ( ) seven years. (for, since)
It's been five years ( ) we met last year. (for, since)
Mike and his parents ( ) the north for half a year.(have been to, have gone to, have been in , have been)