What is the normal duration of a menstrual cycle?

The normal duration of a menstrual cycle typically ranges from 21 to 35 days. This timeframe is considered standard for most women, allowing for individual variation. A cycle shorter than 21 days or longer than 35 days is generally deemed irregular.

The menstrual cycle's length is influenced by various physiological factors, including hormonal fluctuations that regulate ovulation and menstruation. While 28 days is often cited as an average cycle length, many women may experience cycles that fall outside this average yet remain completely normal and healthy.

Choices outside the range of 21-35 days reflect either shorter or longer cycles that are less common, making option B the accurate representation of normal menstrual cycle duration. Therefore, the 21 to 35 days range encompasses a healthy variety of cycle lengths that are typical in the general population.