Which of these is the best indication of the relative age of a rock layer

Could someone me with number one you

Models are non-visual ways of coummincating how someone thinks about something in the natural world

Which statement describes a way in which the digestive and excretory systems work together? a. the nephrons absorb nutrients from food going to the large intestine. b. the excretory system balances blood gases in the small intestine. c. the intestinal villi filter blood and send wastes to the bladder. d. the excretory system balances the salts and water obtained from digested food