Persons suffering from hypertension (high blood pressure) are advised a low-salt diet because

The correct option is B High salt leads to water retention in the blood that further increases the blood pressure
When the salt is present in the blood, the water is reabsorbed by the kidneys and retained in the body. This water will cause an increase in the blood volume thereby, increasing the blood pressure. The person suffering from hypertension is advised to have a diet with low salt content so that there is no more increase in the blood pressure which can result in heart attack.

Thus, the correct answer is option B.