What structures drain the areas in the posterior mediastinum behind the pericardium?

The correct choice is regional lymph nodes because these specific nodes are responsible for draining lymph from the posterior mediastinum, which includes the area behind the pericardium. The regional lymph nodes are strategically located to collect lymph from surrounding structures, facilitating the drainage of fluid and immune responses from this region.

The other structures mentioned, such as chest lymph nodes and bronchial lymph nodes, serve different areas and are not specifically dedicated to the posterior mediastinum. The thoracic duct is a major lymphatic vessel that drains lymph from a broad area of the body into the venous system but does not directly correspond to the targeted drainage behind the pericardium. Regional lymph nodes provide a more localized and specific function in this anatomical context.