Which one of the following statements related to corporate diversification and sustained competitive advantages is not true? a. the fact that a strategy is valuable does not necessarily mean it has sustainable advantage. b. in order for diversification to be a source of sustained competitive advantage, it must be easy to imitate. c. a firm must be organized to implement a strategy to have sustained competitive advantage. d. diversification per se is usually not a rare firm strategy. e. in order for diversification to be a source of sustained competitive advantage, it must not only be valuable, but also rare and costly to imitate.