19. the pia mater layer in the ventricles is rich in blood vessels that produce
a. keratin.
b. csf. c. new skin.
d. dopamine.

Which plains area lies in both the united states and canada? altiplano central canadian shield coastal plains great plains

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

How are fossils most commonly formed