To construct a coherent sentence from parts P, Q, R, and S, a logical connection based on context and flow is required. An analysis of each part is as follows:
Arranging these parts logically yields the sentence: "The citizens faced the calamity during the natural disaster despite the lack of resources and responded with immense courage." The correct order is Q-S-R-P, ensuring a logical progression from the situation, to its timing, the challenge, and the subsequent reaction. The final answer is: Q-S-R-P.