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They were skating when he fell down. / He fell down while they were skating
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She was talking on the phone, when the man took it./ While she was talking on the phone, the man took it.
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She was cooking *baking( when the cooker exploded / The cooker exploded while she was cooking.
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While they were watching TV the heating went out./ They were watching TV when the heating went out.
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While they were rehearsing, the lights went off. / They were rehearsing when the lights went off.
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She was reading a book when the phone rang. / While she was reading a book, the phone rang
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He was peeling the carrot when he cut his finger. / He cut his finger while he was peeling the carrot.
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They were having a picnic when it started to rain. / While they were having a picnic, it started to rain.