The examples of open materials in the given options are:
1. A number-matching game, a coloring sheet, and a truck in the block center.
2. Pieces of fabric in dramatic play, paper plates in the art center, and cardboard tubes in the block center.
Open materials are items that can be used in various ways and do not have a set purpose. They encourage creativity, imagination, and open-ended play among children. In the context of the question, the number-matching game, coloring sheet, and truck in the block center offer versatility in how they can be utilized. Similarly, the pieces of fabric, paper plates, and cardboard tubes mentioned also fit the criteria of open materials due to their potential for diverse uses and creative exploration.