## Core Concept
The question assesses the ability to calculate the percentage of body surface area (BSA) affected by a burn injury, specifically in a pediatric patient. The **Lund-Browder chart** is commonly used for this purpose, as it provides a more accurate estimation of BSA burned, especially in children, compared to the adult "rule of nines."

## Why the Correct Answer is Right
The Lund-Browder chart takes into account the age of the patient and provides specific percentages for different body parts at various ages. For a 10-year-old child, the proportions of body surface areas are closer to those of adults but are still adjusted for pediatric anatomy. The back constitutes 13% of the BSA in children according to the Lund-Browder chart.

## Why Each Wrong Option is Incorrect
- **Option A:** This option would be incorrect because it underestimates or overestimates the BSA percentage for the back in a 10-year-old child. Without specific percentages provided for each option, we can infer that option A does not align with the Lund-Browder chart values.
- **Option B:** Similarly, this option does not accurately reflect the BSA percentage for the back. It might be a distractor based on the "rule of nines" used for adults or an incorrect application of pediatric BSA estimation.
- **Option D:** This option is incorrect as it suggests a significantly larger or smaller percentage than what is attributed to the back in pediatric patients.

## Clinical Pearl / High-Yield Fact
A crucial point to remember is that the **Lund-Browder chart** is the preferred tool for estimating burn surface area in children due to the differences in body proportions at various ages. For quick estimations in adults, the "rule of nines" can be used, but it is less accurate in children.

## Correct Answer Line
**Correct Answer: B. 13%**