Common scab of potato can be controlled by reducing pH below 5.2 is caused by the pathogen

Answer: Option A

Common scabs of potato can be controlled by reducing pH below 5.2 is caused by the pathogen Streptomyces scabies.
Common scab of potato is caused by Streptomyces scabies and occurs throughout the world. It is most prevalent and important in neutral or slightly alkaline soils, especially during relatively dry years. The same pathogen also affects beets, radishes and other root crops.
Scab problems tend to disappear when soil pH is less than 5.2. Therefore, acidify garden soils (i.e., make sure the soil pH is less than 7) to control the infection.