阅读理解。
Wang Xiaojun is 12 years old. He lives in the country in Hubei. Today is his birthday. His parents prepare a
nice dinner for him, but the boy says,"I won't have the dinner because after the dinner, today is over, and my
parents are leaving for Shenzhen tomorrow. I don't want to let them go." Wang Xiaojun spends the birthday
with his parents for the first time in three years. Three years ago, his parents went to Shenzhen to work. They
stayed and worked there to make money. Tomorrow they have to leave home to go to Shenzhen. Wang is not
the only stay-at-home child. In the country of China, there are many children staying at home without (没有)
their parents. Stay-at-home children have a lot of problems. Many of them stay with their grandparents. They
don't get enough care from parents. Some of them don't study well because their parents can't help them with
their study. The Chinese government (政府) now cares about those children very much and is trying to solve (解决) their problems.
根据短文内容,判断正(T)误(F).
( )1. It is Wang Xiaojun's first birthday.
( )2. Wang Xiaojun won't have the birthday dinner because he is not hungry at all.
( )3. There are many stay-at-home children in the country of China.
( )4. Xiaojun's parents will take him to Shenzhen.
( )5. The Chinese government is doing something to solve the problems of the stay-at-home children.
平面内的第III象限中有沿—y方向的匀强电场，场强大小为E。只第I和第II象限有匀强磁场，磁场方向垂直于坐标平面向里，有一质量为m，电荷量为e的电子，从y轴的P点以初速度v0垂直于电场方向进入电场，P点坐标为
，经电场偏转后，与x轴负半轴成一定角度进入磁场，设磁感应强度B的大小为
。求：