When Dr Schmidt-Nielsen and His Colleagues Followed a "Pulse" of 100

When Dr. Schmidt-Nielsen and his colleagues followed a "pulse" of 100% inhaled oxygen through the respiratory system of an ostrich, the oxygen pulse went to the

A) posterior air sacs to the lung and then to the anterior air sacs before being exhaled.
B) anterior air sacs to the lung and then to the posterior air sacs before being exhaled.
C) lung and then to the anterior air sacs and finally the posterior air sacs before being exhaled.
D) lung and then to the posterior air sacs and finally the anterior air sacs before being exhaled.
E) lung and then back out with exhalation-the air sacs were not involved.