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I met my old friend, Jimmy, who has been studying(present perfect continuous) in London since 2005.
FORM
[has/have + been + present participle]
"who" and the phrase after it is called relative clause. It's used to tell us which person.(Jimmy is the person that has been studying in London since 2005)
We use since to say how long something has been happening.How long has Jimmy been studying in London. form: since+the start of a period.*e.g.: Monday, 1985, 12thMay,lunch.
(He started studying in London in 2005, and is still studying there now. )
We use the Present Perfect Continuous to show that something started in the past and has continued up until now. "For five minutes," "for two weeks," and "since Tuesday" are all durations which can be used with the Present Perfect Continuous.
* Not Perfect Present, because the present perfect tense is completed, but related to present, and the present perfect continuous is continued until now.