Final answer:
A bulk oxygen system refers to an assembly of equipment that can hold a capacity of oxygen greater than a certain value, which is 20,000 foot in this case.
Step-by-step explanation:
A bulk oxygen system refers to an assembly of equipment that can hold a capacity of oxygen greater than a certain value. In this case, the capacity is defined as greater than 20,000 foot. So, the correct answer is C) 20,000 foot.