What is a digital platform?

Multiple choice question.

A group of people who are connected to each other by a service or piece of infrastructure that facilitates flows of goods, services, or information

An increase in the value of a product to each user, including existing users, as the total number of users rises

A negative network effect that occurs if a network that has capacity limits becomes filled past those capacity limits

An Internet website or software application $($app$)$ that facilitates interactions between two or more distinct but interdependent sets of users