The correct answer is: A. PSQR
The man who can work very hard when he must work is generally the one who can play most heartily when he has the chance of playing.
In option A, PSQR, the sequence of the sentences is correct. The first sentence, “The man P,” introduces the topic of the paragraph. The second sentence, “is generally the one Q,” describes the man. The third sentence, “who can work very hard R,” provides more information about the man. The fourth sentence, “when he must work S,” completes the description of the man.
In option B, QRPS, the second sentence, “is generally the one Q,” is followed by the third sentence, “who can work very hard R.” This is incorrect because the second sentence should provide more information about the man, and the third sentence should provide more information about the man’s ability to work hard.
In option C, QRSP, the second sentence, “is generally the one Q,” is followed by the fourth sentence, “when he must work S.” This is incorrect because the second sentence should provide more information about the man, and the fourth sentence should provide more information about the man’s ability to play.
In option D, SPQR, the first sentence, “The man P,” is followed by the fourth sentence, “when he must work S.” This is incorrect because the first sentence should introduce the topic of the paragraph, and the fourth sentence should provide more information about the man’s ability to work.