RTOS are designed to handle real-time applications that require a deterministic response to events. The most critical aspect of securing an RTOS is ensuring the availability and timely processing of tasks, which can be crucial for safety and operational continuity in industrial environments. If tasks are not completed within the required time frame, it could result in system failures or hazards. Other answers, such as data leakage and physical tampering, although important for general security, are not as central to RTOS security concerns as availability and timely task execution.