Which of the following determines the T-1 requirements?

The determination of T-1 requirements is fundamentally based on the principle of having no untrained tasks. This implies that to meet T-1 standards, personnel must only perform tasks for which they have received proper training. The rationale behind this requirement is to ensure that individuals are fully competent and capable when performing their responsibilities, thereby minimizing the risk of errors and enhancing overall operational efficiency. Without this foundation of training, the effectiveness and reliability of the operations could be compromised.

In contrast, the other options, while important in their own right, do not specifically address the core requirement for T-1 status. Proficiency levels, such as achieving a minimum percentage, reflect how well an individual can perform assigned tasks but do not inherently ensure that all tasks being performed are within the trained scope. Full completion of all training could theoretically allow for untrained tasks if not monitored properly, and a mix of trained and untrained tasks directly contradicts the essence of what T-1 criteria seek to achieve. Thus, maintaining a standard with no untrained tasks becomes pivotal for guaranteeing a competent workforce.