Mother to child:
[The TV is showing nothing but interference; the child is holding the unplugged aerial and looking confused]
'What have you done?'
[There is paint all over the child's clothes]
'What have you been doing?
'What have you done?' refers to a single event [the child has unplugged the aerial]. 'What have you been doing?' refers to a repetitive or continuous process [painting/making a mess].
Student or Learner