To maintain sustainable competitive advantage a firm must control the following set of exploitabl resources. These resources must be

a$.$ Valuable, rare, tough to imitate, can substitute

b$.$ Zero startup value, rare, tough to imitate, can't substitute

c$.$ Valuable, easily obtained, tough to imitate, can't substitute

d$.$ None of the choices are correct

e$.$ Valuable, rare, imperfectly imitable, non$-$substitutable