1. Unless you study harder, you'll get bad marks

2. If this man isn't a driver, he can't help you move by car

 3.Unless he practices writing  everyday, he can't improve his writing skill

 4.If you don't return  this book to the library today, you will have to pay a fine

 5.If you don't go out more often, you might fall ill 

 6.Unless you aren't absent from school, you have to write a sick-note

 7.If the seas isn't warmer, the ice at the North and South pole will not melt

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6. Unless you are absent from school, you will not have to write a sick-note.

7. If the seas isn't warmer, the ice at the North and South pole will not melt.