● Birds (#1) moving through crops can carry pathogens from the infected plant to other plans. Woodpeckers carry spores of tree pathogens. Some plant pathogenic bacteria are carried to short distance by wind (#4). In some places, rain seems to be more important than insects in disseminating the fire blight bacteria, by its washing or splattering effect of rain. (#3). There is only Option D where 1,3 and 4 are together. So, "D" has to be the correct option.