What service is used by USPS to ship Other Regulated Materials Domestic (ORM-D)?

The correct choice for shipping Other Regulated Materials Domestic (ORM-D) is USPS Retail Ground. This service is designed for items that cannot be shipped via air and are not classified as hazardous materials, but still require special handling. USPS Retail Ground allows for the safe transportation of these materials while also providing economic shipping options for heavier packages.

The other shipping services, such as Priority Mail, Express Mail, and First-Class Mail, are not ideally suited for ORM-D items due to their specific handling requirements. For instance, Priority Mail and Express Mail generally cater to fast delivery options and may not accommodate the particular regulations related to ORM-D items. First-Class Mail, while being a popular choice for lightweight packages, is also unsuitable for ORM-D due to similar restrictions. Thus, USPS Retail Ground is the appropriate service for shipping ORM-D materials domestically, ensuring compliance with safety regulations and effective delivery.