The Following Questions Refer to the Data Shown Below Figure 421
-Birds Have Negative Pressure Breathing, but It Differs from Entering

The following questions refer to the data shown below.
Blood entering a capillary bed of a vertebrate was measured for the pressures exerted by various factors.
$$\begin{array} { l c c } & \begin{array} { c } \text { Arterial End of } \\\text { Capillary Bed }\end{array} & \begin{array} { c } \text { Venous End of } \\\text { Capillary Bed }\end{array} \\\hline \text { Hydrostatic pressure } & 10 \mathrm {~mm} \mathrm { Hg } & 14 \mathrm {~mm} \mathrm { Hg } \\\text { Osmotic pressure } & 26 \mathrm {~mm} \mathrm { Hg } & 26 \mathrm {~mm} \mathrm { Hg } \\\mathrm { PO } _ { 2 } & 100 \mathrm {~mm} \mathrm { Hg } & 42 \mathrm {~mm} \mathrm { Hg } \\\mathrm { PCO } _ { 2 } & 40 \mathrm {~mm} \mathrm { Hg } & 46 \mathrm {~mm} \mathrm { Hg }\end{array}$$
Figure 42.1
-Birds have negative pressure breathing, but it differs from that of mammals and is more efficient because of which of the following reasons?

A) The bird's mouth movements are able to force air into the lungs.
B) The tidal volume in birds is much larger than in a comparably sized mammal.
C) The maximum PO2 is significantly higher in bird lungs.
D) The flow of air in a bird's lungs is from posterior to anterior.
E) The brain of the bird maximizes oxygen uptake more efficiently.