Final answer:
A year of experience is defined as all of the above options: a twelve-month period for low pressure boiler, including off-season maintenance, and 2,000 hours or more of work.
Step-by-step explanation:
For purposes of the exam, a "year of experience" is defined as all of the above options: a) a twelve-month period for low pressure boiler, including off-season maintenance, and b) 2,000 hours or more. This means that a year of experience can either refer to a twelve-month period or 2,000 hours of work, whichever comes first.