Final answer:
The posterior interventricular sulcus contains the coronary sinus, which drains the right and left ventricles, ultimately emptying into the right atrium.
Step-by-step explanation:
The structure that lies in the posterior interventricular sulcus and drains the right and left ventricles is the coronary sinus. This large, thin-walled vein on the posterior surface of the heart resides within the atrioventricular sulcus. Coronary veins, including the middle cardiac vein, drain into the coronary sinus. The coronary sinus then empties directly into the right atrium, carrying deoxygenated blood from the myocardium back to the heart for reoxygenation.
The coronary sinus receives blood flow from several veins that parallel the arteries on the heart's surface. These veins, such as the middle cardiac vein draining the areas supplied by the posterior interventricular artery, and the small cardiac vein draining the posterior surfaces of the right atrium and ventricle, ultimately collect blood from the myocardium and deliver it to the coronary sinus.
Therefore, the correct answer to the student's question is 1) Coronary sinus.