Which of the following is a social networking service?

Concept

A social networking service is an online platform whose primary purpose is to let users create an identity or profile, connect with or follow other users, and exchange content.

Services should be classified by their main function, not merely by the fact that they operate on the internet.

Application

• Twitter primarily enabled public short-form posts, following, and interaction among users.

• Amazon.com primarily provided online retail and marketplace services.

• eBay primarily provided marketplace and auction services.

• Gmail primarily provided email and mailbox services.

Contrast and cross-check

Among the offered services, only Twitter had social networking as its primary role; the others centered on commerce or email.

Result

Therefore, the answer is Twitter.