The major veins of the heart are the coronary sinus, the anterior interventricular veins, left marginal veins, posterior veins of the left ventricle and the posterior interventricular veins. Most of the other veins collect and return blood to the right atrium through the coronary sinus.
If you type that up on ask.com it says.... " Most of the veins of the heart open into the coronary sinus...." Also, you're are supposed to say what are the veins of the heart. In my opinion I think the answer is veins and arteries. Veins bring blood to the heart to get deoxygenated , while arteries bring oxygenated blood to the tissues. Hope it helped! :)