1. The blunder do the underground instrument undergo an undermining of the thunderbolt. �Ǹ�ʧ���õ�������������һ������ƻ���
2. The blunder did the underground instrument undergo an undermining of the thunderbolt. �Ǹ�ʧ���õ�������������һ������ƻ���
3. The author gives out five protecting methods and the importance of protecting the logging equipment from thunderbolt. �����¼���豸Ԥ����Σ��������ͱ�Ҫ�ԣ��Ƽ������ַ�����ʩ��
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n.
1. a discharge of lightning accompanied by thunder
2. a shocking surprise