CIE AS level biology mcq

1 is not correct because blood would leak from left to right, not right to left. The left ventricle pumps oxygenated blood and the right ventricle pumps deoxygenated blood, so the blood in the left ventricle is at much higher pressure. If there is a hole in the septum, the blood will move from a higher pressure to a lower pressure - therefore into the right ventricle. That alone tells you that D must be correct.
2 is correct because the right ventricle pumps blood into the pulmonary artery, to the lungs. As blood is leaking into the right ventricle, more blood is being pumped to the lungs.
3 is correct because less oxygenated blood is making it from the left ventricle to the aorta.