Concept:Jumbled sentence parts must be arranged so the resulting sentence is grammatically correct and meaningful.
Explanation:The subject “rubidium” (part Q) begins the sentence.
Then “in the filaments of” (part P) logically follows.
Next, “photoelectric cells” (part S) completes the noun phrase.
Finally, “which convert light energy into electrical energy” (part R) gives extra detail about the cells.
Thus the correct order is Q → P → S → R, which corresponds to option A (QPSR).
Answer:The correct sequence is QPSR (option A).
The rearranged sentence is: “Rubidium is used in the filaments of photoelectric cells which convert light energy into electrical energy.”