The correct answer is Circulation improves.
This is a short-term benefit that can occur relatively soon after quitting smoking, as the body begins to heal and restore normal blood flow. Other benefits, such as decreased risk of stroke and heart disease, typically develop over a longer period after quitting. The heart rate returning to normal can also be a part of these immediate improvements in cardiovascular health. However, the noticeable improvement in circulation is a specific short-term effect.