Metals experience plastic deformation when a. their crystal patterns have been disrupted by stress
b. electrons have jumped up to the conductive area
c. an electric field has been applied
d. they are immersed in water

Option (A) is the correct answer.

Explanation:

Plastic deformation is the change in shape of an object or metal caused by the load of excess stress.

Thus, metals experience plastic deformation when their crystal patterns have been disrupted by stress.

When stress is provided to the metal then their crystal pattern gets deformed resulting in change of shape of the metal. Plastic deformation is a permanent deformation.