The likelihood is proportional to θ^(−n/2)exp[−Σx_i²/(2θ)−Σx_i−nθ/2]. Only Σx_i² enters its parameter-dependent data term, and the likelihood-ratio criterion makes it minimal sufficient. The pair in C is not complete: E(X̄+S²)=−θ+θ=0 without X̄+S² being almost surely zero. −X̄ is unbiased but not a function of the complete sufficient squared-sum statistic; Rao–Blackwellization improves it. **B**.
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