THE_‚ÄÖ√Ñ√∂‚ÀÖ√Ë‚Àւ§SOCKET‚ÄÖ√Ñ√∂‚ÀÖ√Ë‚ÀÖ¬•_PROTOCOL_IS_PERMITTED_ON_WHICH_OPERATING_SYSTEMS??$#

• A. all
• B. unix only
• C. windows only
• D. none