The nucleus ambiguus is involved in which of the following activities?

The nucleus ambiguus plays a crucial role in the control of muscles involved in swallowing and phonation, which are functions vital for speech and the act of swallowing. Located in the medulla oblongata, it primarily contains motor neurons that innervate certain muscles of the pharynx, larynx, and soft palate via cranial nerves IX (glossopharyngeal) and X (vagus).

This nucleus is essential for coordinating complex motor activities that allow for effective swallowing, enabling the movement of food from the mouth through the pharynx and into the esophagus, as well as controlling the muscles of the vocal cords, which are involved in sound production. This intricate control ensures safe swallowing and clear vocalization, highlighting why this option correctly identifies the nucleus ambiguus's involvement in these specific activities.