Which fitness component do you think is the most important to have and why? listed 5 fitness components: cardiovascular fitness muscular strength muscular endurance flexibility body composition

I would say cardiovascular fitness. Cardiovascular fitness is what makes you able to have muscular strength, and flexibility, and those fitness components.
Cardiovascular fitness is the ability of the heart, blood cells and lungs to supply oxygen-rich blood to the working muscle tissues, and the ability of the muscles to use oxygen to produce energy for movement. It's basically what makes you able to excersise.
~Deceptiøn