Where does the right lymph duct primarily drain fluid from?

The right lymph duct, also known as the right lymphatic duct, is responsible for draining lymphatic fluid from specific regions of the body. It primarily collects fluid from the right side of the head, the right arm, and a portion of the upper thorax. The reason option B is correct is that the right lymph duct effectively serves these areas, ensuring that the lymph is returned to the venous circulation through the right subclavian vein.

In contrast, other options might refer to regions that are drained by different lymphatic structures. For example, the left arm and the left side of the head are primarily drained by the thoracic duct, which handles lymph from the left side of the body. The option referring to both legs and abdomen also corresponds to the thoracic duct, which collects fluid from these lower areas. Lastly, the upper thorax and both arms would include regions that are not completely served by the right lymph duct alone, making those options incorrect in framing the primary drainage function of the right lymph duct.