If a chemical reaction catalyzed by an enzyme is being carried out, and there is a sudden, drastic decrease in temperature, what is most likely to happen next?

Mostly the reaction rate will decrease because the activity of the enzyme hugely depends on temperature. For eg. most of the body enzymes work best at 37 degree Celsius. Many enzymes show highest activity at a particular temperature (usually the body temperature).

option b doesnt seem probable in this case.

option c is also not a good probablity because enzymes don't adapt.

option d seems like option b and hence not probable.