Which of the following is most suitable for teaching children the concept of fractions?

Cuisenaire rods are colored rods of different lengths (1 to 10 units) that visually and tactilely represent number relationships and are particularly effective for teaching fractions. Children can see, for example, that a 2-unit rod is one-half of a 4-unit rod or one-third of a 6-unit rod, making part-whole relationships concrete. The abacus is best for place value and computation, geoboards for geometry, and number charts for number patterns. Cuisenaire rods are specifically designed to make fraction concepts tangible.