Study the diagram of the geologic time scale. Which method is most likely used to identify what happened before the start of the Paleozoic era?

A. Scientists study fossils from the Jurassic period.
B. Scientists observe index fossil records of the Mesozoic era.
C. Scientists examine fossil evidence during the Precambrian time.
D. Scientists explore the emergence of mammals and humans in the Cenozoic era.

What is a difference between systemic and pulmonary circulation? a. systemic circulation carries oxygenated blood to the lungs and pulmonary circulation carries deoxygenated blood to the body. b. systemic circulation carries deoxygenated blood to the lungs and pulmonary circulation carries oxygenated blood to the body. c. systemic circulation carries deoxygenated blood to the body and pulmonary circulation carries oxygenated blood to the lungs. d. systemic circulation carries oxygenated blood to the body and pulmonary circulation carries deoxygenated blood to the lungs.