_______ are one of the most expensive type of structure in general.

Correct Answer : Option (B) :   To reduce breakdowns of critical equipment

Explanation : Maintenance can be divided into different types. Preventive is one of the type of maintenance. It is done with the goal of reducing critical equipment breakdown. It is done periodically and very well planned.

Correct Answer : Option (B) :   Requirements of removing number of major structural elements

Explanation : Easily accessible and reachable parts are primary requirement of maintainability considerations. Accessibility directly affects the effort and maintainability of an aircraft. If a design requires removal of major structural elements to access the component then, it is considered as the worst design based on maintainability.

Correct Answer : Option (C) :   Maintenance of equipment after failure or break down

Explanation : Corrective maintenance is done after breakdown or failure. Maintenance done before breakdown is called preventive maintenance. Scheduled maintenance is similar to preventive.