To whom must the special inspector or inspection agency furnish progress reports?

The special inspector or inspection agency is required to furnish progress reports directly to the building official and to the Registered Design Professional (RDP) in responsible charge. This practice ensures that both the building official, who oversees compliance with codes and regulations, and the RDP, who is responsible for the design and integrity of the project, are kept informed about the progress of the inspection activities.

This direct communication helps maintain accountability and ensures that any issues found during inspections can be addressed promptly by those directly responsible for the project. It reinforces the collaborative nature of construction projects, where clear communication between inspectors, officials, and design professionals is crucial for adherence to safety and quality standards.

Other options, such as reporting only to community stakeholders or the project architect, do not fulfill the essential requirement of keeping those in regulatory authority and oversight fully informed, which is why they are not correct in this context.