Ask for more information
example: i was writing a letter (where?)- where were you writing a letter?
1) He was buying a present for Helen (when?)
2) we were playing ping-pong (where?)
3) they were skating (where?)
4) it was raining (when?)
5) we were staying at a hotel (why?)
6) we were doing the city (with whom?)
7) she was speaking to mr green (why?)
8) she was visiting my grandparents (when?)
9) you were swimming (where?)

When he was buying a present for Helen?Where will we playing ping-pong?Where were they skating?When was it raining? Why were we staying at a hotel?With whom were we doing the city?Why was she speaking to Mr green?When was she visiting my grandparents?Where were you swimming?(я в 4 не очень уверена...)