The correct option is
A Thigh bones elongate
The period of life, when the body undergoes changes, leading to reproductive maturity is called as an adolescence. Human body undergoes various changes marking the onset of puberty. There is a sudden increase in height seen during puberty which is due to elongation of all the long bone of the body, i.e., bone of arms and legs.So, the correct answer is 'Thigh bones elongate'