All of the following increase the risk of breast cancer except —

Correct option is C

Early first childbirth is protective against breast cancer, not a risk factor. Women who give birth at a younger age have reduced lifetime exposure to estrogen, which lowers their breast cancer risk. In contrast, late menopause, obesity (due to higher estrogen from fat tissue), and physical inactivity increase the risk by promoting prolonged estrogen exposure and poor immune regulation.
Explanation of each option: (a) Late Menopause – Extends the duration of estrogen exposure, increasing the chance of breast cell mutations and breast cancer. (b) Obesity – Fat tissue converts androgens into estrogen, elevating levels and increasing cancer risk, especially post-menopause. (c) Early first childbirth – Correct. It reduces total estrogen exposure and promotes differentiation of breast cells, thus lowering cancer risk. (d) Lack of physical activity – Associated with weight gain, hormonal imbalance, and weakened immune response, all contributing to increased cancer risk.