In the following passage , some words have been deleted. Read the passage carefully and select the most appropriate option to fill in each blank.

Aerobics is a system of exercise (1) ______ stimulates the heart and lungs to (2) ______ beneficial changes in the body. These (3) ______ strengthening of the muscles and (4) ______ the rapid flow of air in and out of the lungs; a more (5) ______ heart to pump more oxygen and blood.