The Blood Buffer Reactions Described by H₂CO₃

The blood buffer reactions described by H₂CO₃
<--------> H⁺ + HCO₃- indicate that

A) scientists are uncertain which direction the equation flows.
B) the reaction can flow either direction depending on whether there is too much H⁺ or more H⁺ is needed.
C) any reaction in one direction causes an immediate reverse reaction.
D) chemicals can swing wildly from acidic to basic.
E) the reaction goes back and forth in an unpredictable manner.