I need help on my science test please

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

Which component in a graph indicates an independent factor? a. y-axis b. x-axis c. scale

What are the pros and cons of quadrat sampling?