Which of the Following Conditions Must Be Met If a Firm's

Which of the following conditions must be met if a firm's resources are to be used to achieve a sustainable competitive advantage? 

A)  ​The resources must be cheap, common, and substitutable. 
B)  ​The resources must be fixed assets, such as machinery, buildings, and land. 
C)  ​The resources must be current assets, such as inventory. 
D)  ​The resources must be valuable, rare, imperfectly imitable, and nonsubstitutable.