A、They account for the largest proportion. B、90 per cent of them are reasonable. C、Most of them are for delayed air tickets. D、F

W: Mr. Hiller, is the number of complaints increasing or decreasing?
M: There was a slight decrease last year. The highest number of complaints was two years ago when we received 7,300.
W: Does the reduction mean that the quality of goods and services is improving?
M: [12]I don’t think so. It’s probably due to the poor economic situation. Most people are simply buying less.
W: Is there any change in the nature of the complaints?
M: Not really. People are still complaining about the same things.
W: What do they complain about most often?
M: [13]Electrical appliances. Last year, we received 1,809 complaints about them—25 percent of all complaints. Then there are complaints about travel agencies, photographic and sound equipment, and clothing—in that order.
W: What sort of complaints do you get about travel agencies?
M: Oh, they include anything from air tickets to accommodation.
W: Are most of the complaints justified?
M: [14]About 90 per cent of the complaints about travel agencies are justified. In other areas, investigation of about 50 per cent of the complaints reveals some kind of business malpractice, but overall about 30 per cent of the complaints are due to misunderstandings on the part of the consumer, the rest are too vague to be worth following up.
W: How long does it take you to complete an investigation of a complaint?
M: [15] About two to three weeks for a proper investigation. We really need more staff.
W: Thank you, Mr. Hiller.
M: My pleasure.
12. Why did the number of complaints decrease last year according to the man?
13. What do customers complain about most often?
14. What does the man say about complaints about travel agency?
15.How long does it take the man to complete an investigation of a complaint?