**Core Concept**
Millard's 'Rule of Ten' is a guideline used in the management of infantile hypertrophic pyloric stenosis (IHPS). This rule helps clinicians determine the best time for surgical intervention by considering various factors that contribute to the condition's progression and complications.

**Why the Correct Answer is Right**
Millard's 'Rule of Ten' includes several criteria, such as the patient's weight (A. 10 lbs), the duration of symptoms (B. 10 weeks), and the patient's hemoglobin level (C. 10 gm %). However, the rule does not explicitly mention the patient's age in months (D. 10 months) as a criterion for surgical intervention. This is because IHPS typically presents in infants between 3-6 weeks of age, and the rule focuses on the patient's weight, symptoms duration, and hemoglobin level to guide surgical timing.

**Why Each Wrong Option is Incorrect**
**Option A:** The patient's weight (10 lbs) is indeed a criterion in Millard's 'Rule of Ten', as it helps clinicians assess the patient's nutritional status and potential for complications.
**Option B:** The duration of symptoms (10 weeks) is also a key factor in Millard's 'Rule of Ten', as prolonged symptoms can indicate delayed diagnosis or worsening condition.
**Option C:** The patient's hemoglobin level (10 gm %) is another criterion used in Millard's 'Rule of Ten', as it helps clinicians assess the patient's risk for anemia and potential complications.

**Clinical Pearl / High-Yield Fact**
Millard's 'Rule of Ten' is a useful guideline for clinicians managing IHPS, but it is essential to remember that individual patient factors and clinical judgment should always take precedence in determining the optimal time for surgical intervention.

**Correct Answer:**
✓ Correct Answer: D. 10 months.