Major Internet-Related Firms Such as Google, Apple, Amazon, Microsoft, and Facebook

Major Internet-related firms such as Google, Apple, Amazon, Microsoft, and Facebook each have an area of the market that they dominate. Which of the following is true about their interaction in the market?

A) They tend to act independently, paying little attention to what the other firms do.
B) They collude so that each firm retains a near-monopoly in a particular sector without facing threats from the other major firms.
C) They behave according to a price leadership model, with each firm taking a leadership role in the particular sector it dominates.
D) They compete fiercely, as each looks for ways to increase profits by expanding into rivals' markets.