Concept:Rearranging jumbled parts to form a grammatically and logically correct sentence.
Explanation:The opening phrase "According to an engineer" requires a noun clause next.
Only part Q, "a newly developed air-cooler system", provides a suitable subject.
Thus, Q must be the first part.
Next, part S introduces the relative clause "which is based on a principle radically different from".
Then part R completes the comparison: "that employed in conventional room coolers".
Finally, part P gives the result: "might hit the market next year".
Hence, the correct sequence is Q, S, R, P.
Answer:The proper sequence is Q S R P, which corresponds to option C.