Defends the body after it has been invaded by a microscopic organism

Defends the body after-it has-been Invaded by a microscopic organism
antibodies

Google it it's on quizlethere's the link i used to study

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.