What does ZIP stand for in postal services?

The term ZIP in postal services stands for "Zone Improvement Plan." This concept was developed to improve the efficiency of mail delivery in the United States by providing a system of numerical codes that streamline the sorting and routing process. The ZIP code system allows postal workers to quickly identify geographic areas, thus expediting the delivery of mail. By using a code composed of five digits (and sometimes extended to nine), each ZIP code corresponds to specific regions, making it easier for the postal service to manage logistics.

While the other options might seem plausible at first glance, they do not reflect the officially recognized meaning of ZIP in the context of postal services. The focus of the correct answer is on the improvement aspect, which is essential for the optimization of the postal delivery system.