What is "pair-wise testing" (also known as all-pairs testing)?

A A combinatorial test design technique that generates a reduced set of test cases ensuring that all possible pairs of input parameter values are covered at least once, rather than testing every possible combination B Pair-wise testing requires testing every possible combination of input values exhaustively, with no reduction C It is a testing technique that can only be applied to exactly two test cases total D Pair-wise testing refers only to having two testers work in the same room