**Core Concept**
Congenital hypertrophic pyloric stenosis (CHPS) is a condition characterized by thickening of the pyloric muscle, leading to gastric outlet obstruction. This condition typically presents in infants, with symptoms emerging due to increased gastric pressure and vomiting.

**Why the Correct Answer is Right**
Symptoms of CHPS usually become apparent around 3-5 weeks of age, with the peak incidence occurring at 4-6 weeks. This timing is crucial for early diagnosis and treatment to prevent dehydration and electrolyte imbalances. The exact mechanism behind the delayed presentation of symptoms is not fully understood, but it is thought to be related to the gradual increase in gastric pressure as the infant feeds.

**Why Each Wrong Option is Incorrect**
* **Option A:** 2 weeks - This is too early for symptoms to appear, as the infant's pylorus is still developing.
* **Option B:** 8 weeks - This is too late, as the infant's condition may have progressed to severe dehydration and electrolyte imbalance.
* **Option C:** 1 month - This is a vague answer and does not accurately reflect the typical age range for symptom presentation.

**Clinical Pearl / High-Yield Fact**
The "rule of 3s" can be remembered for CHPS: symptoms typically present at 3-5 weeks of age, with 3% of infants being diagnosed before 3 weeks and 3% diagnosed after 6 weeks.

**Correct Answer: D. 4-6 weeks**