Final answer:
The nurse should prioritize setting consistent limits on the client's harmful ritualistic behavior to ensure their immediate safety, which is the highest priority in planning care.
Step-by-step explanation:
The nurse should prioritize setting consistent limits on the ritualistic behavior if it harms the client or others. Although identifying how the behavior interferes with daily activities, exploring the purpose of the behavior, and helping the client manage anxiety are all important aspects of care, the immediate safety and well-being of the client comes first.
This aligns with the principle of nonmaleficence, which is to do no harm. Hence, option 3 should be the nurse's highest priority when planning the client's care.