In 1940 Bennett discovered that a virus could be transmitted from an infected to a healthy plant through bridging dodder that was parasitizing both plants. It has long been known that dodder haustoria establish cellular connections with the host plant.
Parasitic plant like dodder is used as conduct either for the transmission of viruses or mycoplasma from a host plant to a plant, that is not typically a host or for an agent, that is not graft-transmissible.
So, the correct answer is 'Both A and B'.