When the rate of the reversible reaction A + B <--> C is studied under a certain set of conditions, it is found that the rate of the forward reaction is k[A]. What can be concluded about the rate law for the reverse reaction under these conditions?
(A) Rate = k[C]
(B) Rate = k[C]/[B]
(C) The rate law of the reverse reaction cannot be
determined from the information given.
(D) An error must have been made, since if the reaction
is reversible, the forward rate law must be
Rate = k[A][B].

The answer is B, but I'm confused on why.