Answer:
The correct answer is option B.
Step-by-step explanation:
At 60 to 70 degrees the reaction stops, due to the rise of temperature more than its optimum temperature. At high-temperature molecules of enzyme vibrate more, this vibration breaks the bonds that determine the shape of the enzyme in shape.
The shape of the active site of enzyme changes due to this and the substrate is not fit together with it and the reaction stops.
Thus, the correct answer is - B.