Common scab is checked by

Answer: Option A

Common scab is checked with Wet soil.
A common scab of potatoes is a soil-borne disease caused by the bacteria-like organism Streptomyces scabies.
It's been reported that increasing soil moisture to 80 - 85 percent during tuber initiation until tubers are 1 - 1.5 inches in size can reduce common scab incidence.