The sentence that best conveys the atmosphere of tension and anxiety is "the fate of the nation was riding that night;" as it displays the uncertainty of the outcome and the fate of the nation was on sake. The language and tone employed by the author are very much crucial to determine the meaning and here, the tone implies the ambiguous outcomes that would decide the future of the nation provides a panic-stricken and anxious surrounding to the content. Thus, option third is the answer as it compliments the above claim.
