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When a cashier tell customers that they get a free bonus gift (e.g. poster, sticker) for the goods they bought, how can we say that?
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You're entitled to a bonus gift of ___________.
This CD you're buying comes with a free __________________.
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aramahosithat they get a free bonus gift (e.g. poster, sticker) for the goods they bought
Also,

You get a free ___ with that.

CJ
Students: Are you brave enough to let our tutors analyse your pronunciation?
Comments  
With your purchase of _ , we'll include a free _ .

Although, I would go with CJ's example.

-Karica
Students: We have free audio pronunciation exercises.