The present perfect tense is often used in English to talk about situations that started in the past and are continuing now. We sometimes use the present perfect in a question with ‘how long’ using the words ‘for’ and ‘since’.
* for = throughout (a period of time)
* since = from (an exact point in time) until now
You’ll find a quiz on our website: http://www.bbc.co.uk/learningenglish/english/course/lower-intermediate/unit-12/session-2/activity-1
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