Periodic markets in rural areas are temporary marketplaces established at regular intervals (weekly or biweekly) in various village locations. They fulfill local needs by providing a platform for villagers and small-scale traders to sell agricultural produce and household goods. These markets are typically not permanent and convene only on designated days.
Option A: Incorrect — quasi-urban centers denote small towns, not periodic rural markets.
Option B: Correct — periodic markets take place on specific days at specific rural locations.
Option C: Incorrect — personal and professional services are restricted within such temporary arrangements.
Option D: Incorrect — vendors might source goods from diverse origins, not exclusively from wholesale markets.
Therefore, the correct option is (B): These markets are held on specific days at different locations.