Emma and Hannah are 13-year-old school girls from Minnesota, USA. They are good at making new things and both of them are also good at sales. They are selling charms   made out of bottle caps. The girls came up with the idea last summer when they saw charms were popular with kids. They talked with their parents about the idea. Since then they have sold enough charms to buy a bike for Hannah. The girls collect bottle caps and then clean them. They find some interesting pictures on the Internet or on paper, and then glue them onto the inside of the caps. There are different kinds of pictures. "Peace signs are popular with girls, and single-letter charms are popular with boys whose names start with those letters," Emma and Hannah said. Now, charms can be found everywhere at Dakota Hills Middle School in Eagan. "Students put charms on purses, backpacks, and their lunchboxes," said Emma. Emma and Hannah also have a shop on the Internet. They hope they can sell their charms to more kids. They're thinking about selling their charms at the Eagan Market Festival next summer. Their business is not only for getting money. At their Valentine's sale, 20% of the income   went to charity. Which of the following may NOT be on the charms?
Pictures. Signs. Letters. Numbers.