The correct answer is "High systolic, because when the heart pumps, the pressure inside the aorta would be greatest, causing the weak spot to rupture outward".
High systolic means the pressure generated due to the contraction of heart. As soon as heart will contract it will tend to squeeze out the blood accumulated inside it. Because of this out rush, this blood will enter the aorta and exert great pressure on the walls of the aorta. This high pressure will impact weak spot in the aorta adversely and cause it to bulge out.