What is the law of conser vation of enargy?

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 is the best example of plant tissue? the answer is d (just took the test)

Which of the following molecules could pass through the plasma membrane by simple diffusion? a. na+ ions b. glucose c. amino acids d. carbon dioxide