In the sentence "South Korean students mustn't sleep in the classroom", the modal verb MUSTN'T in this context indicates:
The phrasal verb RELY ON in "Most parents rely on private tutoring ..." (second paragraph) means:
In "lf they find any in class, the owner of the hagwon is punished ... " (last paragraph) the words THEY and ANY refer in the context, respectively, to:
The active voice equivalent to " ... the students are sent home" in the context (last paragraph) is:
Choose the question we would ask to get the following answer: "The school day starts at 8 a.m." (2nd paragraph)