Which of the Following Fundamental Insights Was Provided by Porter's

Multiple Choice

Which of the following fundamental insights was provided by Porter's five forces framework from the completion of the Alta Velocidad Española (AVE) ?

A) A strong threat of substitutes decreases the rivalry among existing competitors.
B) All the five forces must work together to have a meaningful impact.
C) Any of the five forces on its own, if sufficiently strong, can extract industry profitability.
D) Competition must be defined more narrowly to remain confined to the industry's closest competitors.