To those who were familiar with the dam before the flood, the dam's failure was no surprise at all. Option C
The weak structure of the dam and its potential for failure were known to those who had seen it before the flood. In actuality, in the years preceding the flood, there had been multiple alerts regarding the safety of the dam. Therefore, those who were acquainted with the dam did not find it surprising when it failed.
The other options for answers are false. It was not just a political opportunity; underground blasting was not the reason for the dam's failure. The failure of the dam was ultimately caused by structural flaws within it, even though the city council might have been at fault for permitting the structure to continue functioning in its compromised state.