In human females, the event that reflects the onset of the reproductive phase is menstruation.
Explanation: Menstruation is the shedding of the uterine lining, which occurs regularly throughout a woman’s reproductive years. It marks the beginning of the menstrual cycle, signifying that the body is capable of pregnancy.
Why other options are incorrect:
A. Growth of body:
While physical growth is a part of puberty, it doesn’t specifically indicate the onset of reproductive capability. Growth can occur independently of hormonal changes related to reproduction.
B. Changes in hair pattern:
Changes in hair pattern, such as the development of pubic hair and underarm hair, are also part of puberty. However, these changes are hormonal-driven and occur alongside other secondary sexual characteristics like breast development, not necessarily coinciding with the start of menstruation.
C. Change in voice:
Voice changes occur during puberty due to hormonal shifts. While these changes are related to sexual maturation, they are not the direct indicator of reproductive readiness. Menstruation is the more definitive event.