The correct answer is d) medial rotate the shoulder.
The latissimus dorsi is a large, flat muscle located in the lower back that plays a significant role in the movement of the shoulder joint. Its primary functions include extending, adducting, and medially rotating the shoulder. While flexing the shoulder (option a) and elevating the scapula (option b) are actions associated with other muscles such as the deltoid and trapezius, respectively, and abducting the scapula (option c) is not an action of the latissimus dorsi either, medial rotation is indeed one of its key actions.