Rearrange the given sentences to form a meaningful paragraph.

P. However, most executives disregarded her security warnings.
Q. Decades later, her forecasts about cyber threats were completely validated.
R. Elena frequently alerted the board about impending data vulnerabilities.
S. She advised the company to upgrade their infrastructure before a breach occurred.

The correct option is RSPQ.

Step-by-Step Explanation:
1. Sentence R ("Elena frequently alerted the board about impending data vulnerabilities.") introduces the subject (Elena) and sets up the primary context. It acts as the logical starting sentence of the paragraph.
2. Sentence S ("She advised the company to upgrade their infrastructure before a breach occurred.") logically follows R by elaborating on the specific action and advice Elena gave regarding those data vulnerabilities.
3. Sentence P ("However, most executives disregarded her security warnings.") introduces a transition using "However" to contrast Elena's advice with the executives' reaction of ignoring her warnings.
4. Sentence Q ("Decades later, her forecasts about cyber threats were completely validated.") concludes the paragraph by showing the eventual outcome and ultimate proof of her earlier warnings.

Thus, arranging the sentences in the sequence RSPQ forms a coherent and meaningful paragraph.