Plato and Aristotle

Imagine what it must have been like when Aristotle sat at Plato’s feet to learn from him. Plato would say, “Every heart sings a song, incomplete, until another heart whispers back. Those who wish to sing always find a song.” So, Aristotle set out to explore the location from where this voice came and dissected hearts.  However, because he did not count the right atrium, Aristotle considered the human heart to be three-chambered or "triventricular," consisting of the right ventricle, the left atrium, and the left ventricle. In spite of his anatomical misconceptions, which structure would Aristotle have labeled correctly in the image of this heart placed in the anatomical position and then slicing the left ventricle open? That is, which structure is labeled correctly to match the numbered lines?

Select the correctly labeled structure?