In Comparison with Pulmonary Blood Flow at Rest in the Upright

In comparison with pulmonary blood flow at rest in the upright position,pulmonary blood flow when upright during exercise in normal individuals is:

A) Distributed more to the bottom of the lung than to the top.
B) Distributed more to the top of the lung than to the bottom.
C) Distributed essentially evenly between the top and the bottom of the lung.
D) Is too highly variable to be determined.