Final answer:
The option correctly identifying the factor related to heart rate is B. Physical needs, as physical activity and oxygen demand lead to increased heart rate. Hormones like epinephrine and norepinephrine raise heart rate during physical exertion.
Step-by-step explanation:
Among the options given, B. Physical needs are correctly identified in their relationship with heart rate. Physical activity and the body's need for increased oxygen can lead to an elevation in heart rate. Factors such as stress, exercise, temperature changes, and body position changes can also affect heart rate. Hormones like epinephrine and norepinephrine, for instance, can cause the heart rate to increase to meet the body's physical demands.
Additionally, cardiac output, which is influenced by the heart rate, can enhance or decrease blood pressure. When the body requires more blood flow during physical exertion, the heart rate tends to increase in order to pump more blood throughout the body. On the other hand, factors such as high levels of cholesterol and bone density do not directly affect the heart rate in such a straightforward manner as physical demands do.