**Core Concept**
Breast cancer is a complex disease influenced by a combination of genetic, hormonal, and environmental factors. The risk of developing breast cancer can be increased by various predisposing factors, including genetic mutations, reproductive history, and lifestyle choices.

**Why the Correct Answer is Right**
The correct answer is a factor that does not increase the risk of breast cancer. Genetic mutations, such as _BRCA1_ and _BRCA2_, significantly increase the risk of breast cancer. A family history of breast cancer, particularly in first-degree relatives, also raises the risk. Additionally, certain reproductive factors, like early menarche and late menopause, increase the duration of exposure to estrogen, which can stimulate breast cancer growth.

**Why Each Wrong Option is Incorrect**
**Option A:** Early menarche is a known predisposing factor for breast cancer due to the increased duration of estrogen exposure.
**Option B:** A family history of breast cancer, especially in first-degree relatives, is a significant risk factor.
**Option C:** Nulliparity (never having given birth) increases the risk of breast cancer, possibly due to the prolonged exposure to estrogen and progesterone.

**Clinical Pearl / High-Yield Fact**
The risk of breast cancer can be reduced by factors such as breastfeeding, which decreases the duration of estrogen exposure, and maintaining a healthy body mass index (BMI).

**Correct Answer: D.**