**Core Concept**
The National Deworming Program in India aims to control and prevent soil-transmitted helminthic infections in children. Albendazole is a commonly used anthelmintic for this purpose. The program follows a specific dosing schedule for different age groups to ensure effective treatment and minimize side effects.

**Why the Correct Answer is Right**
For children under 2 years old, the recommended dosage of albendazole in the National Deworming Program is 200mg. This dosage is lower than the standard adult dose to account for the child's smaller body weight and to reduce the risk of adverse effects. The lower dosage is also in line with the World Health Organization's recommendations for the treatment of soil-transmitted helminth infections in children.

**Why Each Wrong Option is Incorrect**
**Option B:** 400mg is the standard adult dose, which is too high for children under 2 years old and may increase the risk of adverse effects.
**Option C:** 500mg is even higher than the adult dose and is not recommended for children under 2 years old.
**Option D:** 2 tablets of 400 mg would be equivalent to 800mg, which is also too high for children under 2 years old and may cause harm.

**Clinical Pearl / High-Yield Fact**
When administering albendazole to children, it's essential to use the correct dosage based on the child's age and weight to ensure effective treatment and minimize the risk of adverse effects.

**✓ Correct Answer: A. 200mg**