**Core Concept**
Congenital hypertrophic pyloric stenosis is a condition where the pyloric muscle is thickened, leading to gastric outlet obstruction. This condition often presents with vomiting, which can cause electrolyte imbalances. The underlying principle being tested is the understanding of the pathophysiological consequences of this condition on electrolyte balance.

**Why the Correct Answer is Right**
In congenital hypertrophic pyloric stenosis, the persistent vomiting leads to loss of hydrogen ions (H+) and chloride ions (Cl-), resulting in **hypochloremic metabolic alkalosis**. This condition is characterized by a decrease in chloride levels, an increase in bicarbonate levels, and often accompanied by hypokalemia due to renal losses in an attempt to conserve hydrogen ions.

**Why Each Wrong Option is Incorrect**
**Option A:** Not directly related to the primary electrolyte imbalance caused by vomiting in congenital hypertrophic pyloric stenosis.
**Option B:** Though potassium levels can be affected, this is not the primary electrolyte abnormality associated with the condition.
**Option C:** This option might seem plausible due to the association with vomiting, but it does not accurately describe the specific electrolyte abnormality seen in this condition.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that congenital hypertrophic pyloric stenosis typically presents with **hypochloremic metabolic alkalosis**, which is a critical piece of information for diagnosis and management. Understanding the pathophysiological consequences of persistent vomiting is crucial.

**Correct Answer:** D. Hypochloremia.