Answer the questions using when and the verb of the subordinate clause in the past continuous tense....

1. When did you catch that cold? (skate on a frosty day)
   You caught that cold when you were skating on a frosty day.

2. When did he write those nice poems? (have a holiday)
   He wrote those nice poems when he was having a holiday.

3. When did she learn the language? (live in England)
   She learned the language when she was living in England.

4. When did she hear that song? (listen to a concert on the radio)
   She heard that song when she was listening to a concert on the radio.

5. When did you buy that book? (read up for my exams)
   You bought that book when you were reading up for your exams.

6. When did the boy hurt himself? (ride the bicycle)
   The boy hurt himself when he was riding the bicycle.

7. When did Philip lose his camera? (walk about the city)
   Philip lost his camera when he was walking about the city.

8. When did he ring you up? (have supper)
   He rang you up when he was having supper.

Here are the answers to the questions using "when" and the verb in the past continuous tense:

1. When did you catch that cold? (skate on a frosty day)
   You caught that cold when you were skating on a frosty day.

2. When did he write those nice poems? (have a holiday)
   He wrote those nice poems when he was having a holiday.

3. When did she learn the language? (live in England)
   She learned the language when she was living in England.

4. When did she hear that song? (listen to a concert on the radio)
   She heard that song when she was listening to a concert on the radio.

5. When did you buy that book? (read up for my exams)
   You bought that book when you were reading up for your exams.

6. When did the boy hurt himself? (ride the bicycle)
   The boy hurt himself when he was riding the bicycle.

7. When did Philip lose his camera? (walk about the city)
   Philip lost his camera when he was walking about the city.

8. When did he ring you up? (have supper)
   He rang me up when I was having supper.

This structure emphasizes that the subordinate clause (with "when") uses the past continuous tense to describe an ongoing action that was happening at the time of the main event.