Put the verb into the present perfect. надо подставить 4формы he (take) his exam for half an hour already.they (play volleyball) they (play volleyball) since 2 o'clock.

He has been taking his exam for half an hour already.
they have been playing volleyball since 2 o'clock.

He has taken, He has been taking, He will have been taking, He had taken.
They have played, They have been playing, They will have been taking, they had taken
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