Which is appropriate for initial rate method experiments to analyze an enzyme-catalyzed reaction?
both enzyme and substrate concentrations are constant.
the temperature is varied and the rate is measured.
enzyme concentration is constant and the rate is measured at different substrate concentrations.
substrate concentration is constant and the rate is measured at different concentrations of enzyme.
the substrate and enzyme concentrations are varied inversely with respect to one another and the rate is measured.

Enzyme concentration is constant and the rate is measured at different substrate concentrations.

Explanation:

The initial rate method experiments are carried out to study the effect of substrate concentration on the rate of an enzyme-catalyzed reaction.  

Since the concentration of the substrate keeps on changing during the experiment, the initial rate of reaction is measured for varying substrate concentrations while the enzyme concentration is kept constant.

B

Explanation:

First we will find the rate of a reaction at low concentrations followed by high concentrations by keeping the enzyme concentration constant.