Cross protection is done in citrus against which disease?

Answer: Option A

Cross protection is done in citrus against Tristeza disease.
Cross protection is a type of induced resistance developing in plants against viruses.
Tristeza is one of the very few virus-induced diseases where mild strain cross-protection has been used successfully in commercial production of various tree crops and is currently the only way a citrus industry faced with severe and destructive stem pitting CTV (Citrus Tristeza Virus) can survive.