Final answer:
The correct answer is option 4. The Post Office Construction Agency employed more people than any other agency.
Step-by-step explanation:
Out of the given options, the agency that employed more people than any other is the Post Office Construction Agency. The United States Postal Service is an independent agency of the federal government responsible for providing postal service. It is widely used and employs a large number of people.
The USPS, responsible for mail delivery and associated services, has been a significant employer, contributing to its status as one of the largest civilian employers in the country. With a vast network of postal facilities and a wide range of operational roles, the USPS has played a crucial role in providing employment opportunities to a diverse workforce, making it a notable institution in terms of workforce size and impact on the labor market.