Answer:
option c. viroid control
Explanation:
The chestnut tree in Europe is infected by a fungus called Cryphonectria parasitica that causes a disease called chestnut blight. The disease is controlled by a biological control method called hypovirulence.
The hypovirulence is a virus that attacks the fungal pathogen (Cryphonectria parasitica ) of chestnut tree. This fungal virus decreases the ability of fungal pathogen to cause chestnut blight disease. This technique prevents the chestnut plant after huge destruction of it in Europe.
The pathogen that have virus is introduced naturally over the plant. This reduces the infection and allows the natural growth of trees. Thus, option C is correct.
