A Novel, Unknown Pathogen Is Devastating a Particular Crop, with Nearly

A novel, unknown pathogen is devastating a particular crop, with nearly 100% mortality of infected plants. You find that the spread of disease within infected plants can be stopped by removing the bark and stem tissue (down to the vascular cambium) in a band around infected stems, and that the first signs of necrosis are rings of dead cells surrounding (completely or in part) apparently living tissue. You then assay the cells inside the necrotic rings expecting to find a high concentration of:

A) chitin.
B) double-stranded RNA.
C) AVR proteins.
D) necrotrophic pthogens.