The Following Questions Refer to the Data Shown Below Figure 421
-Hydrogen Ions Produced in Human Red Blood Cells Are

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
-Hydrogen ions produced in human red blood cells are prevented from significantly lowering pH by combining with

A) hemoglobin.
B) plasma proteins.
C) carbon dioxide.
D) carbonic acid.
E) plasma buffers.