Elementary students who eat breakfast have higher grades than those that don't. For this statement, which could be a hidden variable? Check all that
apply.'
A. The income level of the student's household
B. The amount of breakfast consumed
C. The work schedule of the parent or parents
D. Age of the students

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