​Which of the following makes a firm's resources hard to imitate?

A) ​Do not use resources that flow from the firm's unique history
B) Keep the link between resources and advantage simple
C) Resources emanate from a socially complex organizational structure
D) ​All of the above

Resources that emanate from a socially complex organizational structure are harder to imitate as they involve intangible factors such as culture, relationships, and knowledge sharing that are difficult to replicate. Option A is incorrect because using resources that flow from the firm's unique history may make it hard to imitate, but it is not a guaranteed strategy. Option B is incorrect because keeping the link between resources and advantage simple does not necessarily make them hard to imitate.