['2', ')', 'For', 'the', 'γ', '-', 'ray', 'induced', 'DSB', ',', 'the', 'protective', 'effect', 'by', 'AA', 'is', 'a', 'little', 'bit', 'weaker', 'than', 'the', 'case', 'of', 'photo', 'irradiation', '.']