Total Fisher information is 2. For A, expectation g=2θ, so bound=(g′)²/2=2 and variance=2, attaining it. B has variance 1+2θ² while its bound is 2θ²; C has variance 8+32θ² versus bound 32θ²; D has variance 5 versus bound 1/2. Only **A** attains its bound.
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