When she ..... (cook), she .... (burn) herself.
She was cooking, she burned herself.
She ..... (fall) asleep while she .... (knit)
She fell asleep while she was knitting.
He ..... (fall) while he ..... (climb) the ladder.
He fell while he was climbing the ladder
He ... (swim) when the plane .... (crash).
He was swimming when the plane crashed.
When she .... (arrive), they .... (watch) TV.
When she arrived, they were watching TV.
He .... (play) tennis when a tiger .... (attack) him.
He was playing tennis when a tiger attacked him.
She .... (hurt) her back when she .... (lift) the box.
She hurt her back when she was lifting the box.