The mean age at the beginning of the growth spurt in girls is peaking at age

In most girls, the beginning of their pubescent years starts around the age of 9, and ends around 11 1/2.

NOTE: This is the mean. It is not an absolute when a human will start puberty. Everyones body is different in this regard.

So to answer your question:
The mean age at the beginning of the growth spirt in girls is 9, peaking at age 11.5.

Hope this helps! If you have any questions, please just ask!
Chandowd

B. it promoted the powers of the executive branch