**Core Concept**
The dosage of albendazole for treating roundworm infestation in children is determined by the child's weight, not their age. The recommended dosage is based on the World Health Organization (WHO) guidelines for treating parasitic infections.

**Why the Correct Answer is Right**
The correct dosage of albendazole for a 10-year-old child is 400 mg, which is the standard single dose for children weighing between 25-34 kg. This dosage is based on the child's weight, not their age. The medication is absorbed rapidly after oral administration and is excreted in the feces, making it effective against roundworms.

**Why Each Wrong Option is Incorrect**
* **Option A:** 200 mg is the standard single dose for children weighing between 12-24 kg, which is lower than the child's weight in this scenario.
* **Option B:** 600 mg is the standard single dose for children weighing over 60 kg, which is higher than the child's weight in this scenario.
* **Option C:** 800 mg is not a recommended dosage for children with roundworm infestation.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the dosage of albendazole is based on the child's weight, not their age, to ensure effective treatment of roundworm infestation.

**Correct Answer:** C. 400 mg