Grade 10 Grammar Lesson 7 Present perfect continuous

What is the structure of present perfect continuous tense?
When do we use the present perfect continuous tense?
Can we use a since clause along with the present perfect continuous tense?

•  We use present perfect continuous (has been/have been + present participle) to talk about something that started in the past and has been continuing until now. We may use since and for to indicate the period.
•  We also use present perfect continuous to talk about a past action in view of its present results.
•  We usually ask questions with How long.? in the present perfect continuous about an activity in progress.
•  We may also use a since clause to indicate when the activity or situation began.
  

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