Hidden Avoidable Rectangle
Use solution uniqueness, placed digits, and a strong link to eliminate a candidate that would complete an avoidable rectangle.
All candidates have been entered in the empty cells.
Assume that the puzzle has a unique solution. Use the two-place choice for a candidate in A. Placing candidate 9 lets the two digits in A swap. Therefore, another solution exists. That contradicts uniqueness. Candidates 9 marked × can be removed.