**Core Concept**
The question requires the application of the Lund-Browder chart or rule of nines to estimate the total percentage of body surface area (BSA) affected by burns. This chart helps in assessing the severity of burns and guiding fluid resuscitation and other management strategies.

**Why the Correct Answer is Right**
To calculate the total percentage of BSA affected, we need to calculate the percentage of burns on the right upper limb, right lower limb, and the back. The rule of nines assigns a percentage of BSA to each body region: head and neck (9%), each arm (9%), each leg (18%), each front and back (18%), and the genital area (1%). For the 3rd degree burn on the right upper limb, the percentage would be 9%. For the 2nd degree burns on the right lower limb, the percentage would be 18%. For the 1st degree burn on the back, the percentage would be 18%. Adding these percentages together gives a total of 45%.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not provide a clear calculation, making it an incorrect choice.
**Option B:** This option does not consider the different degrees of burns and their respective percentages, leading to an incorrect calculation.
**Option C:** This option does not account for the 1st degree burn on the back, resulting in an underestimation of the total percentage of BSA affected.

**Clinical Pearl / High-Yield Fact**
When assessing burns, it is essential to consider the degree of the burn, as well as the percentage of BSA affected, to guide fluid resuscitation and other management strategies. The Lund-Browder chart or rule of nines is a useful tool for estimating the percentage of BSA affected.

**Correct Answer:** C. 45%