lace。 Young athletes can； for example； learn how to cooperate with others； make friends； and gain other social skills that will be used throughout their lives。 Coaches and parents should be aware； at all times； that their feedback to youngsters can greatly affect their children。 Youngsters may take their parents’ and coaches’ criticisms to heart and find a flaw（缺陷）in themselves。
Coaches and parents should also be cautious that youth sport participation does not become work for children。 The outcome of the game should not be more important than the process of learning the sport and other life lessons。 In today’s youth sport setting； young athletes may be worrying more about who will win instead of enjoying themselves and the sport。 Following a game； many parents and coaches focus on the outcome and find fault with youngsters’ performances。 Positive reinforcement should be provided regardless of the outcome。 Research indicates that positive reinforcement motivates and has a greater effect on learning than criticism。 Again； criticism can create high levels of stress； which can lead to burnout。
本文主题在于强调积极强化对于年轻运动员的作用。前面的部分为铺垫，而在文章末尾才给出主题句。
例三：主题句在文章中间（2002。1）
Some pessimistic experts feel that the automobile is bound to fall into disuse。 They see a day in the not…too…distant future when all autos will be abandoned and allowed to rust。 Other authorities； however； think the auto is here to stay。 They hold that the car will remain a leading means of urban travel in the foreseeable future。
The motorcar will undoubtedly change significantly over the next 30 years。 It should become smaller； safer； and more economical； and should not be powered by the gasoline engine。 The car of the future should be far more pollution…free than present types。
Regardless of its power source； the auto in the future will still be the main problem in urban traffic congestion（拥挤）。 One proposed solution to this problem is the automated highway system。
When the auto enters the highway system； a retractable（可伸缩的）arm will drop from the auto and make contact with a rail； which is similar to those powering subway trains electrically。
Once attached to the rail； the car will become electrically powered from the system； and control of the vehicle will pass to a central computer。 The computer will then monitor all of the car’s movements。
The driver will use a telephone to dial instructions about his destination into the system。 The computer will calculate the best route； and reserve space for the car all the way to the correct exit from the highway。 The driver will then be free to relax and wait for the buzzer（蜂鸣器）that will warn him of his coming exit。 It is estimated that an automated highway will be able to handle 10；000 vehicles per hour； compared with the 1；500 to 2；000 vehicles that can be carried by a present…day highway。
本文头两段指出了不同人对于汽车的前途的不同看法，在第三段，即文章中间才给出主题句，讲解决城市交通堵塞的一个方法是自动高速公路系统。后面两段具体介绍自动高速公路系统是如何工作的。
请读下面的文章并且找到主题句，做出主旨题。
Exercise 1
The biggest safety threat facing airlines today may not be a terrorist with a gun； but the man with the portable computer in business class。 In the last 15 years； pilots have reported well over 100 incidents that could have been caused by electromagnetic interference。 The source of this interference remains unconfirmed； but increasingly； experts are pointing the blame at portable electronic devices such as portable computers； radio and cassette players and mobile telephones。
RTCA； an organization which advises the aviation（航空）industry； has recommended that all airlines ban（禁止）such devices from being used during “critical” stages of flight； particularly take…off and landing。 Some experts have gone further； calling for a total ban during all flights。 Currently； rules on using these devices are left up to individual airlines。 And although some airlines prohibit passengers from using such equipment during take…off and landing； most are reluctant to enforce a total ban； given that many passengers want to work during flights。
The difficulty is predicting how electromagnetic fields might affect an aircraft’s computers。 Experts know that portable devices emit radiation which affects those wavelengths which aircraft use for navigation and communication。 But； because they have not been able to reproduce these effects in a laboratory； they have no way of knowing whether the interference might be dangerous or not。
The fact that aircraft may be vulnerable（易受损的）to interference raises the risk that terrorists may use radio system in order to damage navigation equipment。 As worrying； though； is the passenger who can’t hear the instructions to turn off his radio because the music’s too loud。
Q： The passage is mainly about 。
A） a new regulation for all airlines
B） the defects of electronic devices
C） a possible cause of aircraft crashes
D） effective safety measures for air flight
【题目译文】这篇文章是关于
【答案解析】C。从每段的第一句话可知文章讲述电磁干扰对于飞机安全的影响和飞行事故的可能原因。
Exercise 2
Believe it or not； optical illusion（错觉）can cut highway crashes。
Japan is a case in point。 It has reduced automobile crashes on some roads by nearly 75 percent using a simple optical illusion。 Bent stripes； called chevrons（人字形）painted on the roads make drivers think that they are driving faster than they really are； and thus drivers slow down。
Now the American Association Foundation for Traffic Safety in Washington D。 C。 is planning to repeat Japan’s sucomess。 Starting next year； the foundation will paint chevrons and other patterns of stripes on selected roads around the country to test how well the patterns reduce highway crashes。
Excessive speed plays a major role in as much as one fifth of all fatal traffic acomidents； acomording to the foundation。 To help reduce those acomidents； the foundation will conduct its tests in areas where speed…related hazards are the greatest—curves； exit slopes； traffic circles； and bridges。
Some studies suggest that straight； horizontal bars painted across roads can initially cut the average speed of drivers in half。 However； traffic often returns to full speed within months as drivers become used to seeing the painted bars。
Chevrons； scientists say； not only give drivers the impression that they are driving faster than they really are but also make a lane appear to be narrower。 The result is a longer lasting reduction in highway speed and the number of traffic acomidents。
Q： The passage mainly discusses 。
A） a new way of highway speed control
B） a new pattern for painting highways
C） a new approach to training drivers
D） a new type of optical ill