Veins have a much lower blood pressure than arteries. which of these prevents backflow of blood in veins?

The pharynx is the structure in the body that serves as a pathway of both air and food. how does the body make sure that food does not get into the lungs? the salivary glands secrete enzymes that pull food out of the air pathway. the small intestine pushes the air out of the digestive system. the pancreas breaks down food in the air pathway. the epiglottis closes the air pathway so that food will not enter it.

About __ of the mass of the cell is water

How do the evolutionary chart and the video support the claim that all living things are made up of cells?