**Core Concept**
Silver nitrate is a topical antiseptic used to prevent or treat infections in burns and other wounds. It has a unique property of causing staining of burnt areas due to its chemical composition.

**Why the Correct Answer is Right**
Silver nitrate works by releasing silver ions, which have antimicrobial properties that inhibit the growth of bacteria, fungi, and viruses. When applied to burnt areas, silver nitrate can cause a chemical reaction that results in the formation of a dark brown or black stain. This staining is due to the oxidation of the silver ions, which react with the keratin and melanin in the skin to form a permanent discoloration. The silver ions also have a high affinity for the sulfhydryl groups in proteins, which can lead to the coagulation of proteins and the formation of a black precipitate.

**Why Each Wrong Option is Incorrect**
**Option A:** Sulfamylon, also known as mafenide acetate, is an antibiotic cream used to treat burns and other wounds. While it has antimicrobial properties, it does not cause staining of burnt areas.
**Option B:** Povidone iodine is a topical antiseptic used to disinfect and cleanse wounds. It is not known to cause staining of burnt areas.
**Option D:** Mafenide, also known as sulfamylon, is an antibiotic cream used to treat burns and other wounds. It does not cause staining of burnt areas.

**Clinical Pearl / High-Yield Fact**
When treating burns, it's essential to be aware of the potential for staining caused by silver nitrate. This can be particularly important when managing facial burns or burns in sensitive areas, where the discoloration can be cosmetically significant.

**✓ Correct Answer: C. Silver nitrate**