Final answer:
The swept zone is the interval listed to represent the remaining oil-in-place a waterflood can recover, as it is the area that the water has swept through to displace additional oil.
Step-by-step explanation:
The book likely lists the swept zone (A) to represent the remaining oil-in-place a waterflood can recover. In the context of secondary recovery methods for oil recovery, waterflooding is the process of injecting water into an oil reservoir to displace and push additional oil to the production wells. The swept zone is the area of the reservoir that has been contacted by the injected water, and thus, where the waterflood will have the effect of recovering additional oil.