Concept:Viral diseases in crops have no chemical cure, so the best control is to eliminate the infected plants.Explanation:Bordeaux mixture is effective against fungal diseases, not viral diseases.Crop rotation and recommended spacing only reduce the spread of some diseases but cannot remove an existing virus from infected plants.Removing and burning affected crops destroys the source of the virus and stops it from spreading to healthy plants.Therefore, this is the most effective method of controlling viral diseases in crops.Answer:B. removing and burning affected crops