Correct answer is (a) Effect of co-immobilization
To elaborate: The above graph represents the effect of co-immobilization on the rate of production through a short reaction pathway. The red line represents the enzymes in free solution whereas the red dotted line represents the co-immobilized enzymes showing a much reduced lag phase. When there are more enzymes in the pathway, reduction in lag phase is very much seen. In case, where the pathway is controlled by the initial substrate concentration which cannot be higher than the bulk concentration. But all those intermediates may be raised due to diffusional restriction on their rate of efflux. Arrhenius plots are related temperature and rate of reaction. Effect of pH against rate of reaction always gives a bell-shaped curve. Concentration profile comes into picture when the enzymes are immobilized on spherical surfaces.