Educational programs certified by the Board must divide the education provided into _______.

The correct answer is based on the structure of educational programs that meet certification requirements set forth by the Board. "Tiers" refers to distinct levels of education or training that systematically build upon one another. In the context of educational programs, this tiered approach allows the program to establish a clear progression from basic to more advanced knowledge and skills.

Each tier typically has specific learning objectives, outcomes, and competencies that students are expected to achieve before advancing to the next level. This structured framework ensures that individuals gain comprehensive knowledge and practical skills in plumbing, which can lead to improved job performance and safety in the field.

Other terms, such as "levels," "phases," and "units," may not capture the distinct hierarchical nature that is implied by the term "tiers." For instance, while levels could imply a sequence, they may not clearly denote the foundational layers that tiers represent. Hence, "tiers" is the most accurate term to describe the organization of certified educational programs by the Board.