The correct option is C Mechanism of reaction as well as relative concentration of reactants
In a multistep reaction the order of a reaction is determined by the slowest step which is called rate determining step. This is depends on the mechanism of the reaction. The order of the reaction depends also on the concentration. If the concentration is high, then it practically remains constant. Hence the order with respect to it becomes zero. If the concentration is low, then the order may not be zero.