Cardiorespiratory Fitness (CRF) is the ability of the & respiratory systems to supply oxygen to skeletal muscles during sustained physical activity. a
muscular
b
lymphatic
c
nervous
d
circulatory

Circulatory

Explanation:  

Cardiorespiratory Fitness refers to the ability of the respiratory and circulatory systems to deliver oxygen to skeletal muscles during exercise. Exercise contributes to these systems being more efficient by enlarging the heart muscle, allowing a greater pumping of blood. Exercise is not only beneficial to the respiratory system, but the heart also benefits from this.

Cardiorespiratory Fitness has a series of benefits for the well-being of the person. Among its benefits is the reduction of diseases such as lung cancer, heart disease, stroke, and others. For these benefits to begin to be noticed, it is necessary to do physical activity 3 to 5 times a week.