Past continuous vs. past simple
'when' + Past simple = Iets gebeurde tijdens een andere activiteit.
''When the phone rang, she was writing a letter.''
'' What were you doing when the earthquake started?''
Past continuous + 'while' + Past continuous = twee doorgaande activiteiten op het zelfde moment.
''What were you doing while you were waiting?''
''I was studying while my father was making dinner.''