Answer:
The heart is a pump, usually beating about 60 to 100 times per minute. With each heartbeat, the heart sends blood throughout our bodies, carrying oxygen ... It sends out an electrical signal to start the contracting (pumping) of the heart muscle.
Explanation:
The most well known answer according to my bio teacher is nitrogen
The macromolecule would probably be the carbohydrate.
Answer:
i can't see what the photo says :(
