Why does a company's strategy tend to be a "work in progress" and evolve over time?

Multiple Choice

due to the changing nature of employee skills and capabilities

because the change in the company's vision and values cause a constant adaptation of the strategy, with the ongoing need to imitate new strategic moves by the industry leaders

because of the ongoing need to imitate the strategic moves of the industry's strongest rival

because of changing circumstances and ongoing management efforts to improve the strategy

because the competitive advantage potential of developing a new strategy changes annually