The right answer is A.
Enzymes play a central role in the regulation of biological processes. They generally consist of protein molecules derived from the translation of the genome, with the exception of ribozymes consisting of RNA. The enzymes intervene by decreasing the energy barrier between the reactants allowing to accelerate the reactions thousands of times more than in the absence of catalysis.
It is true that we can make the analogy between enzyme-substrate and lock-key. But we must take into account that the substrate will be transformed into a product, so the "key" will be somehow "deformed".
