Answer:
Incentive
Explanation:
Incentive -
It refers to the peice or work or activity that enables you to perform the work , is referred to as incentive .
It is a type of motivation or a bait .
Hence , from the given scenario of the question ,
Ordering the bobble head dolls , which is completely not required is a type of incentive , as it will make the shipping free of cost .
Hence , the correct answer is incentive .
