Final answer:
The correct answer about the frequency of purging liquid oxygen (LOX) tanks is not provided based on the options. Consultation of official standards and safety regulations is necessary to determine the appropriate purge cycle for LOX storage tanks.
Step-by-step explanation:
The question regarding the purge cycle of liquid oxygen (LOX) storage tanks does not provide the correct answer within the given options. Therefore, it is not possible to give an accurate answer as to whether LOX tanks should be purged every 90, 120, 240, or 365 days without additional information such as industry standards, regulatory guidelines, or specific operational protocols for the tanks in question.
If the student requires this information for educational purposes, they should be directed to consult their textbooks, course materials, or reliability standards such as those from the National Fire Protection Association (NFPA) or other applicable safety guidelines. Additionally, it's essential to understand that the maintenance and operational procedures for LOX storage might vary depending on the specific use case, scale, and country regulations.
Professional guidelines and standards are crucial for safe operation, and any servicing of a LOX tank should only be done by trained and qualified individuals.