In Paige's scrapbook, she has completed 40 of the 50 pages. Each page is part of a spread, and each spread has a left and a right page. Twenty-five pages will have journaling, where she writes to explain what was happening when the pictures were taken. On a few of the pages she has also included a souvenir of some sort. One third of the pages have a thin border, one third has a thick border, and one third has a graphic border. Which is a uniform probability model for the scrapbook pages?

A. completion
B. souvenirs
C. color
D. journaling