Electrocardiograph (EKG or ECG) technicians operate equipment that measures, monitors, and graphically traces the electrical activity of the heart. Physicians use the graph (electrocardiogram/EKG/ECG) to diagnose and monitor patients' heart problems.
Answer:
Usually, Populations have a genetic variation among individuals, which is important to the population's ability to survive in different situations that have an effect on the natural selection. There are different factors which can increase or decrease the genetic diversity, and influencing natural selection.
These factors include an environmental factor, one of the major factors, which may cause changes in the genetic variation of a population and influence the natural selection. A famous and important example of environmental factors affecting natural selection was during the Industrial Revolution, when many more grey moths made up the moth population.
This was so that they could blend in with the soot from factories to avoid predators.
They Increase the surface area available for the absorption of nutrients
C. because stimuli is how your body responds to something, and in this case, someone's heart rate increases WHEN their blood oxygen drop. Do you see how it responds? ;-)