Which hypothesis most likely explains the results at 60°c and 70°c

The correct option is B. The Enzyme or substrate has been changed.

Explanation:

Enzymes can be described as biological catalysts which speed up a reaction. Each enzyme is specific for a particular substrate. Enzymes work best at a particular pH and temperature known as optimum pH and optimum temperature.

As the temperature is raised, the working of the enzyme enhances. It becomes most efficient at a particular temperature which is known as the optimum temperature. If the temperature is raised beyond this optimum temperature, then the working of the enzyme starts to decline. Eventually, the enzyme loses its shape and is not able to fit the substrate into its active site. So, activity of the enzyme stops.