In the question given below, a sentence is given, divided into parts. One of the parts may contain an error. Identify the part that contains the error, and mark it as the answer. Ignore errors of punctuation. In case the sentence is correct as it is, mark option (e), that is, 'No error'. With four deaths so far, the coal mining tragedy in Assam’s Dima Hasao district has revived a long-standing debate on the hazard nature of rat-hole coal mining in India.