Question

The age at which menstruation begins varies from 9 to 18 years whereas in united states it is about 12 years and 8 month and in india, it is around 12 years2,3.adolescent age shows various societal differences with respect to socioeconomic, environmental, nutritional and geographical area

Answer 1

Hey buddy, here is your answer.

First of all, tell the question so that anyone can help you.

Answer 2

Beause of evolutions drifts and hormone levels