Periodic markets in rural areas are temporary marketplaces that are held at regular intervals (weekly or biweekly) at different village locations. They serve local needs by allowing villagers and small-scale traders to sell agricultural produce and household items. These markets are usually not permanent, and people gather only on fixed days.
Option A: Incorrect — quasi-urban centres refer to small towns, not periodic rural markets.
Option B: Correct — periodic markets occur on specific days at specific rural locations.
Option C: Incorrect — personal and professional services are limited in such temporary setups.
Option D: Incorrect — sellers may collect goods from various sources, not just wholesale markets.
So, the correct answer is (B): These markets are held on specific days at different locations.