### Output Format:
You must output valid JSON. Do not add markdown or conversational text. Three fields:
- answer: Answer to the problem. Letter (A-D) identifying which image best completes the sequence based on full problem analysis, comparisons between shapes, colors, orientations, and relations in rows and columns of the matrix.
- confidence: Confidence in your answer, ranging from 0.0 to 1.0. (1.0 meaning absolutely confident, 0.5 meaning not so sure, 0 meaning purely guessing)
- rationale: Short version of the rationale for your answer.