The first menstruation is called:

The correct answer is Menarche 

Explanation: 

• The reproductive cycle in the female primates (e.g. monkeys, apes and human beings) is called menstrual cycle.
• The first menstruation begins at puberty and is called menarche.
• In human females, menstruation is repeated at an average interval of about 28/29 days, and the cycle of events starting from one menstruation till the next one is called the menstrual cycle.
• Menarche usually occurs between the ages of 9 and 15, though the average age is around 12 or 13. Various factors can influence the timing of menarche, including genetics, nutritional status, overall health, and environmental factors.

Other Options:

• Menopause: Menopause is the stage in a woman’s life when menstrual periods permanently stop, and she is no longer able to conceive naturally. This typically occurs between the ages of 45 and 55, with the average age being around 51. Menopause is diagnosed after a woman has gone 12 consecutive months without a menstrual period. This stage marks the end of the reproductive years and is associated with a decrease in the production of hormones such as estrogen and progesterone by the ovaries.
• Diapause: Diapause refers to a period of suspended or delayed development in insects, some invertebrates, and certain fish or plants that allows them to survive unfavorable environmental conditions.
• Ovulation: Ovulation is the process in the menstrual cycle where a mature egg is released from one of the ovaries. Typically, this occurs around the midpoint of the menstrual cycle, about 14 days before the start of the next menstrual period in a typical 28-day cycle. After its release, the egg travels down the fallopian tube, where it may be fertilized by sperm. If fertilization does not occur, the egg disintegrates, and the menstrual period follows as the uterine lining sheds.