how DoEs thE proFEssor EmphAsizE his point ABout ForCE ClAssiFiCAtion
A、By stAting thE DEFinition AnD ComponEnts oF EACh CAtEgory.
B、By ExplAining thE rElAtionship BEtwEEn thE two CAtEgoriEs.
C、By iDEntiFying thE mEmBErs oF EACh CAtEgory.
D、By CompAring thE FEAturEs oF thE two CAtEgoriEs.