2. If you don't study, you will fail. (UNLESS)

Solution: The word 'unless' means 'if not'. We need to rewrite the sentence using 'unless' instead of 'if... not'.

Explanation:

• The original sentence is: 'If you don't study, you will fail.'
• 'Unless' replaces 'if... not'. So, 'if you don't study' becomes 'unless you study'.
• The structure becomes: 'Unless + subject + verb (present simple), main clause (future simple)'.

Answer: Unless you study, you will fail.