Evaluate the validity of the Resolution rule: From A∨BA \lor BA∨B and ¬A∨C\neg A \lor C¬A∨C, we derive B∨CB \lor CB∨C.
Invalid, requires AAA and ¬A\neg A¬A to be the same variable.
Valid, this is the standard resolution principle.
Invalid, the result should be A∨B∨CA \lor B \lor CA∨B∨C.
Valid, but only if B=CB=CB=C.