The correct answer is: A. RSQP
The correct sequence of the sentences is:
R. There were too many people and too much huge luggage all around.
S. It was shut all night, as usual.
Q. As usual, I got angry about the window.
P. Most people wanted it shut and I wanted it open.
R. The quarrel left me completely upset.
S1. I usually sleep quite well in the train, but this time I slept only a little.
The first sentence (R) sets the scene by describing the crowded and uncomfortable conditions on the train. The second sentence (S) confirms that the window was shut, which is what caused the argument. The third sentence (Q) explains why the speaker was angry about the window: he wanted it open, but most of the other passengers wanted it shut. The fourth sentence (P) provides more detail about the argument, saying that it was a quarrel. The fifth sentence (R) describes the emotional impact of the argument: it left the speaker completely upset. The sixth and final sentence (S1) summarizes the speaker’s experience, saying that he slept poorly on the train because of the argument.
The other options are incorrect because they do not follow the correct sequence of events. Option B (SQPR) puts the quarrel before the argument, which is not possible. Option C (SQRP) puts the quarrel after the emotional impact of the argument, which is also not possible. Option D (RSPQ) puts the quarrel after the speaker’s experience, which is not possible.