1.I don't know her number.I can't ring her
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2.I didn't know her number.I couldn't ring her
If..........................................................................................................
3.The policeman showed me the way.I found the house.
If.........................................................................................................
4.I was not hungry.I didn'tm eat anything
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5.The driver in front stopped so suddenly.The accident happened
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6.I didn't know that Lan had to get up early.I didn't wake him
If..............................................................................................................
7.the sun was shining.We went to the beach yesterday
If........................................................................................................