如图在第一象限内的y轴和直线x=1.0 m之间有一匀强磁场区域，磁场方向垂直坐标平面向外，磁感应强度B=2T，在直线x=1.0 m右侧有沿），轴负方向的匀强电场，电场强度为E =2.5×10⁵ N/C。放置在原点的离子源在纸面内沿不同方向向第一象限不断发射比荷为1.0× 10⁶C/kg，速度均为v₀=1.0×10⁶m/s的粒子，粒子通过磁场区域后都平行x轴射入电场。求：

（1）粒子在磁场中运动的轨道半径；

（2）在x轴上有粒子穿过的区域；

（3）磁场区域的最小面积。

阅读理解。

     [1] Teenagers who spend hours in front of the television may have a poorer diet, a new study shows. It is

not clear, researchers say, whether television itself is the reason, but it is possible that things like snacking in

front of the TV or seeing ads for junk food influence young people's diets.

     [2] The study included nearly 1,400 high school students. It showed that those who watched TV for five

hours or more every day had less healthy diets than other students five years later. As a group, they ate fewer

fruits and vegetables, but ate more fast food, snack products and fried foods.

     [3]"We're not able to tell why," lead researcher Dr. Daheia J. Barr-Anderson said."But we have some

speculations(推测)." People who spend a lot of time in front of the TV, especially teenagers, may have more

snack. It may influence their long-term diet quality. It's also possible that TV ads for fast food, sweets and

snacks make teenagers eat more of those foods. TV time might also replace exercise time for some kids.

     [4] The researchers found a clear relationship between TV time during high school and diet quality of the

young. The heaviest TV viewers five years later, and those who'd watched fewer than two hours every day

had the most fruits and vegetables.

     [5] According to Barr-Anderson, the findings support experts' advice that children should watch no more

than two hours of television every day."Parents should cut the TV time." Barr-Anderson said. She advised that

parents set a good example by eating right, being physically active and controlling their own TV time.

1. Complete the following sentence according to the underlined one in Paragraph 3.(no more than 5 words) 

    Some children may spend much time watching TV instead of _____.

2. What does" it" refer to in Paragraph 1 line2 mean? (no more than 3 words)

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 3. According to Barr-Anderson, what should parents do to set a good example for their children?

    (no more than 15 words)

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4. Fill in the blank in Paragraph 4 with proper words. (no more than 6 words)

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5. What is the passage mainly about? (no more than 12 words)

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