A．The relationship between mice, rats and monkeys.
B．The relationship between diet and animals.
C．The relationship between diet and man.
D．The relationship between diet and healt

A．The heart pumps blood in two directions.
B．The blood is circulated round the body in one direction only by the pumping action of the heart.
C．The blood moved with a backward and forward motion.
D．The heart pumps blood in all directions.