Based on the information provided, the most likely difference between Oscar and Pedro's tooth fairy traditions would be: B. Where they put the tooth.
What is the difference?
The text mentions that Oscar put his tooth under his pillow and this is a common tradition in many Western countries, including the United States.
Children in other countries often have different traditions for lost teeth. For example, children in Spain may toss their teeth onto the roof, throw them towards the sun, or hide them in a glass of water.
So, while both Oscar and Pedro may believe in the tooth fairy, the tradition of where they place their tooth is likely to be different.