The Reaction: a + 3B $\rarr$ D + F Was Studied Carefully and the Mechanism Below

The reaction: A + 3B $\rarr$ D + F was studied carefully and the mechanism below was determined. What is the rate law for the reaction? Hint: Express the rate limiting step in terms of reactants present in the overall reaction.

A) rate = k[A]²[B]
B) rate = k[A][B]²
C) rate = k[C][B]
D) rate = k[A][B]³
E) rate = k[A][B]