Passage: "The office introduced an online appointment system for permit applications. Before the change, applicants lined up as early as five in the morning, and many had to return the next day. Now, applicants choose a time slot online and receive a reference number by text message. Walk-in applicants are still accepted, but they are served only after those with appointments. Some senior citizens complained that the system was difficult to use, so the office set up a help desk at the entrance." Why did the office set up a help desk?
Correct answer: D. Because some senior citizens found the system difficult to use
The last sentence explains that some senior citizens complained the system was difficult, "so the office set up a help desk". "So" signals the cause-and-effect link.
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