Consumers Are Increasingly Showing a Preference for Fulfilling Their Product

Consumers are increasingly showing a preference for fulfilling their product needs via smartphone applications and online shopping. The relative ease of creating a web-based storefront is posing a significant threat to brick-and-mortar retailers and driving many established retailers to close their doors. According to Michael Porter, this is an example of

A) threat of new competitors.
B) supplier power.
C) buyer power.
D) threat of substitutes.