**Core Concept**
The Lund-Browder chart is a widely used method to estimate the total body surface area (TBSA) involved in burns. This chart takes into account the anatomical differences in body proportions between adults and children to provide a more accurate estimate of TBSA.

**Why the Correct Answer is Right**
To estimate the TBSA in a child, the Lund-Browder chart is used. For a 6-year-old child, the chart indicates that the head and trunk account for approximately 30% of the body surface area. Therefore, in this scenario, the estimated TBSA involved would be around 30%.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not account for the anatomical differences between adults and children.
**Option B:** This option is incorrect because it provides an estimate that is too high for a child's head and trunk.
**Option C:** This option is incorrect because it provides an estimate that is too low for a child's head and trunk.

**Clinical Pearl / High-Yield Fact**
A key point to remember when estimating TBSA in children is that the Lund-Browder chart should be used to account for anatomical differences, as adult charts may overestimate the TBSA involved.

**Correct Answer:** D. 30%