Final answer:
The order of the reaction with respect to ClO2 is zero, as evidenced by the unchanged reaction rate when the concentration of ClO2 remains constant.
Step-by-step explanation:
The order of the reaction with respect to ClO2 can be determined by analyzing the changes in concentration and the corresponding changes in reaction rate. By comparing experiments 1 and 2, where the concentration of ClO2 remains constant and the reaction rate remains unchanged, it suggests that the order with respect to ClO2 is zero. Therefore, the correct answer is B) 0.