Хотелось бы прояснить момент. Write general questions for these sentences using the past continuous. Don't forget about question marks. Example 0. Sam was having lunch. Answer 0. Was Sam having lunch? 1) 1. Richard was working in the garden. 2) They were eating a cake. 3) Henry was listening to the radio. 

1) Was Richard working in the garden? 2) Were they eating a cake? 3)Was Henry listening to the radio?
Просто выносим глагол-помошник на первое место (was/were), далее подлежащее и глагол с окончанием ing