Final answer:
The recommended position for postural drainage of the left upper lobe - anterior lung segment is supine, which helps in the effective drainage of secretions by utilizing gravity.
Step-by-step explanation:
For postural drainage of the left upper lobe - anterior lung segment in an adult, the recommended position is supine (option C). In this position, the patient lies on their back with their arms, including palms, touching the sides, and their lower limbs also touching at the sides. This positioning allows for gravity to assist in the drainage of secretions from the anterior aspect of the upper lobe of the left lung. The thoracic duct is a large duct that drains lymph from the body, including the left thorax, but it is not directly relevant to the technique of postural drainage. Options such as right side-lying, left side-lying, or the Trendelenburg position are not recommended for draining the left upper lobe anterior segment as they do not position the lung segment to take advantage of gravity for effective drainage.