Final answer:
The left ventricle, left atrium, and interventricular septum are supplied by the left coronary artery, which includes the circumflex artery and the anterior interventricular artery or LAD.
Step-by-step explanation:
The vessel that supplies blood to the left ventricle, left atrium, and the interventricular septum is the left coronary artery. This artery branches out into the circumflex artery that follows the coronary sulcus and the anterior interventricular artery, also known as the left anterior descending artery (LAD), which follows the anterior interventricular sulcus. These arteries provide the necessary blood flow to the left side of the heart, and ensure an oxygen supply for the myocardium.
The right coronary artery, while important for the right side of the heart and specific areas such as the right atrium and portions of both ventricles, does not supply the left ventricle, left atrium, or the interventricular septum. Therefore, the correct answer to the question is 1) Left coronary artery.