Enzyme catalysis requires a suitable temperature. At the optimum temperature, the catalytic efficiency of the enzyme is the highest. The optimum temperature of amylase is about 37°C. At this time, the catalytic activity of the enzyme is the highest. Starch What is decomposed is excessive. Low temperature can inhibit the activity of the enzyme. As the temperature rises, the activity of the enzyme can be gradually restored. High temperature, over-acidity, and over-alkali can change the spatial structure of the enzyme and permanently inactivate the enzyme. ．

So choose: B.