Final answer:
The concentration of CO will decrease as the reaction moves toward equilibrium because reactants are converted into products, hence option C is correct. Without additional context, it is assumed that O2 concentration will also decrease, which means option B is incorrect and option D is incorrect as O2 concentration would typically not increase.
Step-by-step explanation:
Based on the given information and the principles of chemical equilibrium, the concentrations of CO (carbon monoxide) and O2 (oxygen) will change as the reaction proceeds. As the reaction moves toward equilibrium, the concentration of the reactants, in this case CO and O2, will generally decrease. This is because as the reaction progresses, reactants are converted into products, which leads to an increase in the product concentrations and a decrease in the reactant concentrations.
Therefore, the correct answer is: C. The concentration of CO will decrease. And since O2 was not specifically mentioned in the examples provided, we can infer based on general principles of chemical equilibrium, without additional context about the specific reaction involving O2, that the concentration of O2 will also likely decrease unless it is being replenished in some way. Therefore, option B is incorrect, and option D is also incorrect since the O2 concentration typically would not increase as the reaction proceeds.