Which of the Following Best Describes What a Group Buy

Which of the following best describes what a group buy tool does?

A) Enables the shopper to show products by most viewed,most favorite,or most commented.
B) Publishes customer testimonials.
C) Is dedicated to a group of people who meet online to communicate about products and help each other solve related problems.
D) Is a collection of special offers,sometimes maintained and updated by user submissions.
E) Provides an opportunity for people to join together to qualify for volume discounts.