Which of the following conditions can lead to metabolic acidosis?

Ketoacidosis is a condition characterized by the accumulation of ketone bodies in the blood, resulting in a decrease in blood pH, which leads to metabolic acidosis. This condition primarily arises in individuals with uncontrolled diabetes mellitus, particularly type 1 diabetes, where the absence of insulin prompts the body to break down fat for energy, producing ketones as a byproduct. The excessive buildup of these acids overwhelms the body's buffer systems, causing a significant decrease in bicarbonate levels and leading to a state of acidosis.

In contrast, asthma and chronic obstructive pulmonary disease (COPD) are primarily respiratory conditions that can lead to respiratory acidosis, particularly during acute exacerbations or during severe episodes of breathlessness. Hypertension, while it can have various systemic effects, is not directly associated with metabolic acidosis and typically does not lead to a decrease in blood pH in the same manner that ketoacidosis does. Thus, ketoacidosis stands out as a key direct cause of metabolic acidosis.