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"I was driving when I saw Cathy" I know is correct how about
1. "When I was driving, I saw Cathy"
For me, when it comes to using "when" in past progressive,it should go with simple past like the first sentence...how about if I change it to " While I was driving, I saw her..Is this correct?Using while instead of when?and is it ok if i use that sentence in formal writing?Thanks!
past progressive 
Linear Mode
