Consider the Equilibrium a + B $\leftrightarrows$ C What Is Significant About the Reaction Quotient When [B]

Consider the equilibrium A + B $\leftrightarrows$ C. What is significant about the reaction quotient when [B] = [C]?

A) only that [B] = [C]
B) [A] = [B] = [C]
C) [B] = [C] = K
D) [A] = K
E) The reaction must run in the forward direction.