WHICH_METHOD_CAN‚ÄÖ√Ñ√∂‚ÀÖ√Ë‚ÀÖ¬•T_BE_USED_FOR_EXPRESSING_RELATIONAL_KNOWLEDGE??$#

• A. Literal system
• B. Variable-based system
• C. Attribute-based system
• D. None of the mentioned