Which of the Following Statements Concerning the Experimental Determination of Reaction

Which of the following statements concerning the experimental determination of reaction rates is incorrect?

A) To determine reaction rates one of the reactants must be colored.
B) Monitoring changes in reactant or product physical properties is a convenient way to determine reaction rates.
C) Analysis of samples withdrawn from the reaction solution at varying times is useful for slow reactions.
D) Instrumental methods,such as visible spectroscopy,may be used to continuously measure changes in reactants or products.
E) Any method of analysis that can determine product or reactant concentrations during the course of the reaction can potentially be used to determine reaction rates.