... rather than just recalling all 9 forms, I find it much ... blindly trying to memorize all 9 of them. Seeing a grouping ... relationship**: #3 **A→B→C**, #4 **A←s→B→C**, #5 ... that #3 is _A→C_, #4 is _A←s→C_, and ... 3: Valid Arguments 6 to 9** – deals with **A** being ...