Q: The first period of the paleozoic era was called what? Choices: - carboniferous - permian - ordovician - cambrian A:
cambrian

Q: In the presence of oxygen, hydrogen can interact to make what? Choices: - carbon - helium - acid - water A:
water

Q: The entry of acidic chyme into the duodenum stimulates the release of what? Choices: - progesterone - gastrin - oxygen - secretin A:
secretin