Which of the following conditions leads to an excessive loss of acid, resulting in Metabolic Alkalosis?

Vomiting leads to an excessive loss of stomach acid, primarily hydrochloric acid (HCl), which is produced in the stomach for digestion. When a person vomits, they expel this acid, resulting in a decrease in hydrogen ions (H+) in the bloodstream. This loss of acid increases the pH level of the blood, pushing the body's pH towards alkalosis, hence causing metabolic alkalosis.

Other conditions listed, such as diarrhea, lead to the loss of bicarbonate, which can result in metabolic acidosis rather than alkalosis. Dehydration primarily affects fluid balance but does not necessarily cause an acid-base imbalance directly. Cardiac arrest can lead to a variety of acid-base disturbances mostly characterized by acidosis due to hypoxia and inadequate circulation, rather than directly causing metabolic alkalosis.