He (break) his leg when he (ski).
He broke his leg when he was skiing.
He (fall) asleep while he (read) a book.
He fell asleep while he was reading a book.
He (swim) when he (see) a shark.
He was swimming when he saw a shark.
He (cook) when the fire suddenly (start).
He was cooking when the fire suddenly started.
His friend (text) him while he (do) his homework.
His friend texted him while he was doing his homework.
He (run) when he (slip) on a banana.
He was running when he slipped on a banana.
They (meet) Henry while they (go) home.
They met Henry while they were going home.
He (eat) dinner when his mum (call) him.
He was eating dinner when his mum called him.
They (have) a picnic when it (start) to rain.
They were having a picnic when it started to rain.