Posology

Step 1: Understanding Dilling’s formula.
Dilling's formula is used to calculate the child's dose based on the adult dose, using the child’s age and the standard age ratio. The formula is: In this case, the adult dose is 200mg and the child's age is 12 years.
Step 2: Applying the formula.
Step 3: Conclusion.
The correct answer is (C) 120mg as per Dilling's formula.