How does sublingual nitroglycerin benefit a patient experiencing angina pectoris?

Sublingual nitroglycerin is primarily used for the relief of angina pectoris, and its effectiveness lies in its ability to relax blood vessels. When taken sublingually, nitroglycerin is rapidly absorbed into circulation, leading to the dilation of both coronary and peripheral blood vessels. This vasodilation reduces the workload on the heart by decreasing the amount of oxygen the heart muscle requires, as well as increasing blood flow to the heart itself. The relaxation of blood vessels helps alleviate the chest pain associated with angina by improving oxygen supply to the heart while reducing the heart's demand for oxygen.

This mechanism is why the option indicating that it relaxes blood vessels is the correct answer. The other options relate to effects that are not characteristic of sublingual nitroglycerin's intended use or do not directly address the mechanism by which it relieves angina.