When hydrogen is broke down what 2 substances are created

Veins have a much lower blood pressure than arteries. which of these prevents backflow of blood in veins? a. pressure applied by the heart b. one–way valves in veins c. thin muscular walls of veins

Which of the following is a period in the paleozoic era? devonian cambrian permian all of the above

Which group of protists would be most likely to have cilia as adults and why? (1 point)the sporozoan protists would since they have to spread their spores around.the heterotrophic protists would since they use them to gather food.the parasitic protists would since they need to find other organisms to attack.the autotrophic protists would since they must move to find light.