BUG+n
Use solution uniqueness to eliminate candidates incompatible with every extra candidate in an otherwise bivalue grid.
All candidates have been entered in the empty cells.
Assume that the puzzle has a unique solution. If every extra candidate in A were false, every unsolved cell would have two candidates and two solutions would remain. Therefore, at least one extra candidate in A is true. Candidates 5 and 8 marked × can be removed.