The selling of article from place to place on foot is

Explanation

Itinerant trading refers to the practice of selling goods by traveling from one place to another on foot. This could be done by carrying the goods on the person's back or using a cart or other means of transportation. Itinerant traders often sell their goods directly to customers in different locations, such as in markets or on the streets. They may specialize in selling specific types of goods, such as food, clothing, or household items.

Mailorder, Option A, refers to a method of buying and selling where orders are placed through mail or online and the goods are delivered to the customer's address. This does not involve traveling from place to place on foot.

Barter, Option C, is a type of trade where goods or services are exchanged directly without the use of money. It does not involve traveling from place to place on foot.

Self-service, Option D, refers to a retail method where customers select and purchase goods themselves without the assistance of a salesperson. This also does not involve traveling from place to place on foot.

Therefore, the correct option is B: Itinerant trading.