The correct answer is D. QSPR.
The sentence is about a man who realizes that he has been let down by a colleague whom he had stood by all these years. The correct sequence of the words is:
Q: Little did he realize
S: that he had been let down
P: by a colleague whom he had
R: stood by all these years
The word “little” indicates that the man did not expect to be let down. The word “realize” indicates that he came to understand something that he had not previously understood. The word “let down” indicates that the man was disappointed or betrayed. The word “colleague” indicates that the man was betrayed by someone he knew and trusted. The word “stood by” indicates that the man had been loyal to the colleague. The word “all these years” indicates that the man had been loyal to the colleague for a long time.
The other options are incorrect because they do not follow the correct sequence of the words. Option A, RPSQ, is incorrect because the word “stood” comes before the word “by”. Option B, RSQP, is incorrect because the word “stood” comes after the word “by”. Option C, QSRP, is incorrect because the word “realized” comes before the word “that”.