Question

Molly's breasts are beginning to develop, she is beginning to grow pubic hair, her skin is becoming more oily, and her body is growing rapidly. these changes are brought about by the secretion of _____ by the _____.

Answer 1

These changes are brought about by the secretion of estrogen and androgens by the ovaries.
The ovaries start producing these hormones which are responsible for these changes that Molly is experiencing. Her puberty is just starting, which means that her body is getting "modified" so as to accommodate her new alterations.