ДОПОМОЖІТЬ БУДЬ ЛАСКА, ДАМ 100 БАЛІВ!!
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Ответ:

1) When mother entered his room, he drew a picture.
2) When her aunt aired the room, she caught cold.
3 While I was talking on the phone, my pets were playing in the garden.

Объяснение:

We use when in the Past Simple and while in the Past Continuous.
Ми використовуємо when у Простому Минулому часі, а while у Минулому Тривалому часі.