In the penultimate question, the speaker says 'What do you want me to do next?' This tells us that they have finished chopping the onions and so the present perfect simple is needed; the present perfect continuous would tell us that the job is not yet finished.
In the last question, the focus is on the activity (chopping) and its effects rather than the result (a pile of onion ready for use), so the continuous form is preferred.
Hello quoc hung,
In the penultimate question, the speaker says 'What do you want me to do next?' This tells us that they have finished chopping the onions and so the present perfect simple is needed; the present perfect continuous would tell us that the job is not yet finished.
In the last question, the focus is on the activity (chopping) and its effects rather than the result (a pile of onion ready for use), so the continuous form is preferred.
Peter
The LearnEnglish Team