The first menstrual flow begins at puberty and is termed:

Correct option is D

Sol. Menarche is the first menstrual bleeding experienced by a female, typically occurring between ages 10 to 14. It signals the start of reproductive ability and marks a major milestone of puberty.
Explanation of each option: • (a) Chromosome – Structures within cells that carry genetic material. They play a role in determining biological traits, but are unrelated to menstruation. • (b) Menopause – The permanent cessation of menstruation, usually after age 45. It marks the end of reproductive life, unlike menarche which is the beginning. • (c) Sex chromosome – These determine the sex of an individual (XX for females, XY for males), but they do not signify the onset of menstruation. • (d) Menarche – Correct. It is the first menstrual period indicating sexual maturity and the start of the female reproductive cycle.