阅读理解 It's true that teens don't get enough sleep, but changing the school starting time would have a chaotic _ effect and throw everyone off balance. Scientists have shown that teens are more active later at night than children and adults, so most teens are probably staying up later for whatever reasons.'The researchers measured the presence of the sleeppromoting hormone (荷尔蒙) in teenagers' saliva (唾液) at different time of the day.They learned that the hormone levels rise later at night than they do in children and adults-and remain at a higher level later in the morning.Measuring the hormone in the saliva is a good way to show that most teens have sleep problems, but changing school schedules isn't the best way to fix this.Most people arguing against changing school schedules would say that it would only cause teens to stay up and wake up later, thus leaving them with the same problem. The biggest problem schools would come across from changing their schedules would be the after school and job conflicts students and teachers would meet.'Teachers reported that students were more alert, and research showed that afterschool sports and jobs would suffer.Students in that area might have been able to deal with less time for jobs and sports somehow, but some of them have practice and earlier plans that would become conflicted if this change were to occur.Most students rarely have time to play a sport and do homework before 9 or 10 o'clock.Opening schools later may have worked for some areas, but the reality is often very different. 1. The meaning of the underlined word 'chaotic'in the 1st paragraph is close to________. A. positive B. apparent C. negative D. ambiguous 2. Most teens have sleep problems because________. A. they are more active than children and adults B. school work takes up most of their time C. their hormone levels are higher later at night D. they probably like staying up for no reason 3. Which of the following is TRUE according to the passage? A. There are many conflicts between students and teachers. B. Some of the teachers have practice and earlier plans. C. Most students are able to do sport and homework before 9?00. D. Ways to solve students' sleep problem vary from area to area. 4. The passage mainly develops by________. A. giving reasons B. showing examples C. comparing facts D. offering solutions