**Core Concept**
Tanner's staging is a widely used classification system to describe the sequence of pubertal development in children. It encompasses physical changes such as breast development, pubic hair growth, and genital maturation. The correct answer requires an understanding of the anatomical and physiological changes that occur during puberty.

**Why the Correct Answer is Right**
During Tanner stage III of pubertal development in females, breast development advances to form a secondary mound due to the growth of the areola and papilla. This stage is characterized by the areola and papilla forming a more prominent mound, which is a result of the growth of Montgomery's tubercles and the increased size of the papilla. The growth of the areola and papilla is driven by the increased levels of estrogen during puberty.

**Why Each Wrong Option is Incorrect**
**Option A:** This stage is actually characterized by the beginning of breast development, where the areola and papilla are not yet forming a secondary mound.
**Option B:** There is no Tanner stage that specifically describes the formation of a secondary mound without the growth of the areola and papilla.
**Option C:** This stage is actually characterized by the peak of pubertal growth, where the breast development has already progressed to stage III.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Tanner's staging is not a linear progression and can vary between individuals. The correct staging of breast development is crucial for assessing the pubertal status of children and adolescents.

**Correct Answer: C. Tanner stage III.**