In the context of blood pressure measurements, represents the pressure within the arterial system when the heart is resting and filling with blood.

The numerator in the fraction of the blood pressure measurement is called the systolic blood pressure which is the gauge of the amount pressure your blood is exerting against your artery walls when your heart pumps blood. The denominator is, on the other hand, called diastolic pressure which is the pressure your blood is exerting against your artery walls while the heart is resting between beats. Answer is the diastolic pressure. 
 

The  answer is b since it all happens under ground