**Core Concept**
Hyperchloremic acidosis is a type of metabolic acidosis characterized by an excessive loss of bicarbonate ions (HCO3-) and a concomitant gain of chloride ions (Cl-), leading to an increase in plasma chloride concentration and a decrease in bicarbonate concentration. This condition often arises from gastrointestinal or renal disturbances.

**Why the Correct Answer is Right**
The correct answer, **RTA (Renal Tubular Acidosis)**, is a group of disorders characterized by impaired renal acidification, leading to hyperchloremic acidosis. RTA occurs due to defects in the distal tubules or collecting ducts of the kidneys, preventing the excretion of hydrogen ions (H+) and the reabsorption of bicarbonate ions (HCO3-). This results in a decreased bicarbonate reabsorption and increased chloride reabsorption, ultimately causing hyperchloremic acidosis.

**Why Each Wrong Option is Incorrect**
* **Option A:** RTA is the correct answer, so this option is incorrect.
* **Option B:** Diarrhea is associated with **metabolic alkalosis**, not acidosis, due to the loss of hydrogen ions (H+) and the gain of bicarbonate ions (HCO3-).
* **Option C:** DKA (Diabetic Ketoacidosis) is a type of **ketoacidotic** metabolic acidosis, characterized by an increase in ketone bodies, not hyperchloremic acidosis.
* **Option D:** Dehydration can lead to **metabolic acidosis**, but it is more commonly associated with lactic acidosis or ketoacidosis, rather than hyperchloremic acidosis.

**Clinical Pearl / High-Yield Fact**
Remember that hyperchloremic acidosis is often associated with renal tubular acidosis (RTA), and it's essential to consider the underlying cause of the acid-base disturbance when managing patients with this condition.

**Correct Answer: A. Renal Tubular Acidosis**