By age 20, a person's bones stop growing
a. bone-forming cells are no longer present.
b. less calcium is present in the body.
c. hormones cause the growth centers at the ends of the bones to degenerate.
d. bone cells receive less oxygen and nutrients at that time.

By age 20, a person's bones stop growing because hormones cause the growth centers at the ends of the bones to degenerate. The correct option among all the options that are given in the question is the third option or option "C". I hope that the answer has come to your help.

explanation:

two years ago, when picking flowers in the mountains back of yosemite valley, i found a book. it was blotted and storm-beaten; all of its outer pages were mealy and crumbly. the paper seemed to dissolve like the snow beneath which it had been buried, however; many of the inner pages were well preserved. and although all were more or less stained and torn, whole chapters were easily readable. this is the condition of the great open book of yosemite glaciers today; its granite pages have been torn and blurred by the same storms that wasted the castaway book.two years ago, when picking flowers in the mountains back of yosemite valley; i found a book. it was blotted and storm-beaten, all of its outer pages were mealy and crumbly. the paper seemed to dissolve like the snow beneath which it had been buried, however, many of the inner pages were well preserved. and although all were more or less stained and torn; whole chapters were easily readable. this is the condition of the great open book of yosemite glaciers today, its granite pages have been torn and blurred by the same storms that wasted the castaway book.

Answer bursitis;