In one kind of abnormal chromosome inheritance called down syndrome, a child has three copies of
a. chromosome x.
b. chromosome 21.
c. chromosome y.
d. chromosome 23.

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