Why does CNOT scheduling matter in surface-code syndrome extraction?

Question: In surface-code syndrome extraction, why can the ordering of CNOT gates around a syndrome ancilla matter? A) It determines whether the surface code uses qubits or qutrits B) It can orient correlated hook errors so that they do not reduce the effective code distance in the dangerous direction C) It removes the need for repeated syndrome rounds D) It makes all measurement errors impossible Correct: B Explanation: Faults on ancilla-mediated checks can propagate into correlated data errors. Careful CNOT scheduling controls the orientation of such hook errors so that a single fault is less likely to mimic a low-weight logical error. Topic: advanced quantum computing / surface code / syndrome extraction