1 Grandma was cooking when the doorbell rang/ was ringing / wore ringing
2 When I did / was doing / were doing my homework, my mum called me
3 The builder was working when his boss arrived / was arriving / were arriv
4 When we were coming/ was coming / came in the receptionist was havi
5 We was saying / said / were saying goodbye when the train left the stati
6 When I was buying her book, I saw / see I was seeing the author.​