Which of the following is NOT a classification of E-Commerce?

Correct option is B

E-Commerce (electronic commerce) is the activity of electronically buying or selling of products on online services or over the Internet.
 B2C (Business-to-Consumer) Direct-to-consumer or business-to-consumer is the business model of selling products directly to customers and thereby bypassing any third-party retailers, wholesalers, or any other middlemen.
 D2D (Distributor-to-Distributor) is a way where a state distributer transport/sell to the district distributor. So, D2D (Distributor-to-Distributor) is not a classification of E-Commerce.