The correct option is B They have reduced plant to plant contact.
Aeroponics is the process of growing plants in a closed or semi-closed environment without the use of soil. When the soil is used, a disease can spread throughout the growth media, thus infecting many plants. In most aeroponics, the solid media requires sterilization after each crop and the media is simply discarded and replaced with fresh, sterile media. Aeroponics, hence limits disease transmission as plant-to-plant contact is reduced. Thus the correct answer is option A.