As a person becomes more aerobically fit,the heart's ability to pump out more blood per beat increases in efficiency.This is referred to as

A) heart rate.
B) stroke volume.
C) respiratory exchange ratio.
D) atrial fibrillation.

Stroke Volume

The amount of blood pumped by the left ventricle of the heart in one contraction.

Aerobically Fit

Refers to a state of physical fitness characterized by improved efficiency of the cardiovascular system in absorbing and transporting oxygen.

Blood

A vital fluid in humans and animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away.