Citrus greening caused by the

Answer: Option A

Citrus greening is caused by Fastidious bacteria.
Citrus greening disease is a disease of citrus caused by a vector-transmitted pathogen. The causative agents are motile bacteria. The causative agents are fastidious phloem-restricted, Gram-negative bacteria in the gracilicutes clade.
The disease is vectored and transmitted Needham made the 1^st report of nematode associated with plant disease in 1943 by the Asian citrus psyllid, Diaphorina citri, and the African citrus psyllid, Trioza erytreae, also known as the two-spotted citrus psyllid.